You know what I don’t understand? What “clearly heterosexual” means. Unless someone has stated they are heterosexual I am not going to assume. The same goes for any person or character that has had a homosexual relationship. So, as much as I don’t ship these two I am confused by why anyone thinks anyone is “clearly” any sexual orientation unless they — or, with fictional characters, I will accept their creator or writer or what have you depending on the canon stating it without it ever being brought up in canon — specifically say “I’m straight” “I’m gay” “I’m asexual” “I’m pansexual” etc.
I don’t understand the superfamily thing either, I don’t ship Steve and Tony, but I’m not about to stomp on their fun. Just consider it an AU and ignore them. Don’t follow people who actively ship something you don’t like or figure out what they tag and blacklist that. No you can’t unsee it or anything, but they’re fictional characters and therefore cannot be bothered by people shipping them.
The thing that bothers me about when people pair guys together like this though is how often female characters get thrown under the bus for it. Superfamily is a wonderful example of this because movie!Tony is clearly in a relationship with Pepper — who I never see in any of these things — and Peter is being taken away from Aunt May (and Uncle Ben too in cases of his “adoption” happening when he’s younger). So I’m confused why the problem so many people seem to have is that the fictional characters are “clearly” straight and I so rarely see any complaints about how any female important to these guys is always cut out of the picture.