If you don't want to do the lvl1 botbushfight, don't. (I love it, it's a blast, but I'll only do it if the teamcomp's right). If I don't want to do it and I'm playing with 2 randoms, I just head directly to top lane at the start.
If you're nowhere near bot bush well before they engage, 80% won't engage. If they do, they're doing it knowing it's a 2v3. That's just dumb, and it's them not being teamplayers, not you. But get your ****ed sandwich BEFORE the game, not during it's start.
If you *never* want to do the fight, just let them know in the team chat, and again in game chat while they start their suicide dash. They'll probably abort.