To me some of this goes back to your earlier statement of "Don't treat me like an idiot." It depends a lot on the author's skill. In real life almost anyone that you talk to will have something that they feel strongly enough about that they will "preach" or push their views about it even if it's just the fact that they don't think anyone else should "preach" or push his or her views on them. If this is all the author is showing then I'm fine with that. If it's the main character, especially in a first person POV, then it rapidly gets annoying.
The thing about first-person POV is there seems to be a huge degree of implicit sympathy that comes with it, and if you want to show your first-person protagonist as flawed, particularly flawed in ways they don't realise themselves, you either have to make those flaws so colossal they essentially define the character (as for example Jeff Lindsey's Dexter), or you risk people not seeing them (as witness, well, any of countless arguments I have had in the on-topic part of the forum in which I think JB is illustrating something about Harry's flaws and weaknesses, and other forumgoers disagree from perspectives based to some extent on assuming JB intends Harry to be sympathetic.)
If it's someone that the story sets up as wise and/or "someone that should be listened to" and they are pushing a certain viewpoint, then it begins to feel that the author is pushing that viewpoint.
How long do you give an author to illustrate that they are subverting that before putting the book down ?
Does it help any to suggest that a rant might not be intended seriously if, say, a first-person character is visibly drunk when they go off on it ?
I find this very annoying. I started one series about a woman from our world that finds herself transported to another reality where she has magical powers. I know this is one of the oldest tropes out there but I still enjoy it when it's well done and this was well done. In the fourth book in the series, the main character switches to someone that had been a minor character up until then. It is revealed that the previous protagonist had died, off camera, between books three and four. It was not a gimmick. She was dead and never came back. I never finished the series.
Hmm. That's the kind of bravery from an author that would definitely make me want to read on; I generally appreciate authors who take chances even if they do not work over authors who play safe, at technical and structural levels.
I think part of it is that I have a really strong dislike for stories where protagonists get protected by different rules from everyone else just because they are protagonists.
Titanic for example, where the two leads appear to be playing by Indiana Jones rules when it comes to wasding through icy water but everyone in steerage is dying from exposure much more realistically. I can't connect to protagonists who are safe because they are protagonists, and nor can I connect to protagonists who are supposedly in danger if no serious consequences of danger ever happens to them.