No person that you know, under almost any condition, would break an accused murderer from out of jail. It isn't a rational response.
It is under certain circumstances.
1. You have the means to do so.
2. You believe you can get away with doing so. I mean, not just pulling off the escape but believing you can avoid the legal repercussions.
3. You believe what you are doing is right; and people are capable of believing a lot of crazy s**t, or simply not caring about right and wrong.
There are plenty of historical examples of individuals and groups of supposedly responsible people doing far worse. The case of the FBI agents who covered up for the gangster Whitey Bulger; over a long period of time while he committed numerous crimes and multiple murders, are a prime example. I personally know a former District Attorney who knowingly protected a rapist from prosecution because he thought he was getting more valuable information to convict a group of supposedly worse individuals. (I don't mean he gave this person a lighter sentence, I mean almost complete protection from prosecution.) I also know a couple of police officers (The detectives who investigated the rapes allegedly committed by individual in question.) who discussed putting a hit on that same rapist because they thought they would be doing "the right thing." And they thought they could get away with it.
Family is important, but Harry has more at stake with a daughter, then a single man. This is all well and good if Harry's destiny is to become King of the world, but kinda shortsighted if not.
I don't know what Jim is trying to accomplish but his motivations are kinda lame. I could see going to the wall while Thomas hangs out in a cell. Instead he has the Swart whatevers execute Thomas with a slow death, even though they say he is awaiting judgement. It's just plain stupid and doesn't hang together very well.
I don't blame Harry for his feelings, but I would have preferred it if Harry had a better justification for them. He knew that Thomas was set up, but couldn't prove it or something similar. However, the actual breakout was something that Lara wanted and that Harry was obligated to help her accomplish. He didn't really have a choice in the manner. What would have been far darker would have been if Lara hadn't asked Harry for any favors, if he had just volunteered to help Lara without being compelled to do so.
I do understand what you mean by it feeling a bit lame, like events didn't hang together very well. What bothered me more was that Harry wasn't asking questions beyond, "Why would Thomas do this?" Once Harry realized that Thomas didn't have a rational reason, other than perhaps he had been pressured by someone or something else to do it in order to protect Justine, Harry didn't go any further. Simple questions like "Why was Etri the target?" or "Could it have been an inside job?" or even "Isn't it convenient that Mab told Harry he owed paying off two favors to Lara just before she needed them to rescue Thomas?" are all ideas that should have been floating through Harry's mind, even if he didn't have a way to immediately start investigating any of them. Even if none of those ideas led anywhere, they would have been great misdirection for the readers to ponder over. At least it would have been things the Harry we used to know would have done. He is supposed to be a detective after all.
And why is Harry all of a sudden having abandonment issues? He's picked a piss poor time to get all angsty about being left in a lurch. Hell Thomas should be angry, his mother left him after making sure he was a serial killer by birth.
Oh, I think this has been coming on for a long time. Harry has had almost nothing good to say about being an orphan (and why would he?), at any time during the series. He didn't know that Ebenzer was his grandfather until well after he had grown up and moved to Chicago or this would have most likely come out pre-Storm Front when Harry was a teenager living with Ebenezer.
Now add that to the old anger that Susan once kept Harry's daughter a secret and hidden from him, the realization that Ebenezer was thinking of doing the same thing and that the Winter mantel with its territorial imperative was pushing Harry to fight, and it was easy for Harry to run with his feelings.
Your point about Thomas is not invalid. If the series was about the lives of two characters; Harry and Thomas and each of them shared the story's narration, I think we would hear a lot more of what Thomas thinks and feels about Margaret LaFey. Jim covers this by making Thomas go silent and angsty when he gets angry or he feels something is too personal to discus.
Putting that aside for the moment, having Thomas suffer the pain of all the many that he has hurt has been something that has been needed. As sympathetic as he is he has committed murder multiple times and being Harry's brother doesn't make him fit company for a child. Eb is right, down the line and Harry is wrong. Lara is a 1000 year old murderess who has had to have killed hundreds. And even she admits she can't always control it. Harry and Jim are in a fantasy. In the real world Lara and Thomas would be hunted by their prey and exterminated.
Minor question, but is Lara 1,000 years old? Where did you get that info? I just checked the Dresden Files Timeline and I didn't find a reference for her date of birth. Is it from something Lara said in one of the books?
As far as Thomas being made to suffer all the terrible things he has done to others, I think you are correct. Other forum members have guessed that this is a part of Thomas' redemption arc and I agree with them.
Ebenezer may be right about the White Court, but what he was thinking about doing was wrong. There is a difference between being right and being self righteous; especially if that attitude leads someone to the point where they can do absolutely anything they feel is right no matter how much it may harm other people. Several people on this forum have posted the idea that perhaps Ebenezer has been slowly corrupted by his use of the Blackstaff, that it doesn't completely shield him from the effects of using black magic. I think it's far more likely that having and repeatedly using this ability over more than two centuries is the corrupting influence. I think "power corrupts" was actually said by Harry or Karin during one of their conversations in Peace Talks, so perhaps it's one of the themes Jim is playing with in this book and the larger story of both PT and Battle Ground.
The Dresden Files is a fantasy series, but you're not wrong about Lara. I think someone with Lara's abilities would have to be incredibly discreet; far more than we see in the series, to enslave and knock off victims without having numerous family members attempt to track her down and kill her.