In short: How do I tell my boss I don't want to join this team, or how do I negotiate conditions for joining if needed be?
Long version:
There's a group in my company who is responsible for developing a product (say product B) I was originally not involved, but was supposed to incorporate it in a different application I'm building (say product C).
At least one person in this group is someone I'm in very bad personal terms with, and he even explicitly asked our manager that I wouldn't be involved in another precursor project (say product A) that needed to be integrated within product B. The manager agreed, and this guy was very arrogant and disrespectful to me about it. I've complained to the manager about his attitude. I was then assured that he indeed had his request granted (something in the lines of "I don't care how he does it as long as he delivers"), and given his later behavior, I'm sure no serious advertence were given to him from our manager.
After that, I've adopted a "not my problem" philosophy related to products A and B, focusing first on independent parts of product C. And, to my knowledge, this team should be doing some nice job on product A, but they're failing to integrate it with product B, and product B in general is being very poorly executed.
Hence, some people on the team started suggesting that they should use parts of my project to compose and validate product B (which are parts I haven't even started). And my boss even considered making me joining product's B team.
I've tried to deal with this professionally, and scheduled a meeting with this team to share some ideias (no management involved). They were very dismissive of my ideas, didn't contribute much of their work, and even gave me some very vague answers to questions that probably should have been answered with "I don't know" or "We haven't done that yet". They even claimed to have finalized a milestone, only to admit this wasn't the case when I've asked about some specific parts of it.
So basically, they'll likely need to redo/finish much of their work on product B, and also do a lot to validate parts of it. I think they are on a path for failing their delivery, but they haven't been honest about.
While this indeed blocks me from finishing product C, which is currently my responsibility, it also puts me in a very uncomfortable position. I really don't want to be part of their failure, and it would be hard to be the whistleblower on their fake progress. Most importantly, I don't feel like working with them personally (though I like, and I'm in good terms with most people in project B). It would also be very difficult to implement all the testing they've skipped.
Much worse, that guy has almost zero knowledge on the frameworks of product B, so he's been basically trying to tell other people what they should do on it (because he can't do it himself) and giving strong opinions to management (even about project C, without consulting me first). Because many people on project B are interns or recent graduates, while he's mid level, people generally comply, and management doesn't care. But I'd hate to be bossed around by a guy who made a serious point he doesn't want to work with me. I'd also dislike finishing almost every meeting with "this is a crappy idea, do it yourself if you think otherwise".
On a large meeting with our boss and other senior management involved, some people in team B have shown interest in me joining them. But I think that was just for the show (they're likely pressed to ask for help, and they've been insisting on hiring new staff), so I'd look bad in case I respond that I don't want to cooperate with them.
I'm considering to have a private call with my boss (the whole company is working remotely). I'd like to frame this situation from a business point of view, but having me join their team does have business sense. Nonetheless, I think it would be just too disrespectful of him to just force me into working with a guy he previously granted the option of not working with me (for known social issues). I would also look like "the difficult guy" if I asked the other guy to be kicked out. Finally I would also sound very unprofessional to start pointing the problems and poor choices that have been made on project B. Our boss hates to be involved in technical meetings, so it would also be a hassle to have him closely involved in all my meetings.
My current ideia would be asking my boss not to make me join them immediately, manifest that while I don't feel like joining them, I would be professional about it, but that the rest of the team should be held to some professionalism standards too. I can also propose that I'll start working on related parts, that they can reuse. I'm afraid I'd just sound like the "not a team player" and that the boss would basically do nothing about it.