ABC Line camping is tricky; some maps have good ABC lines, others don't. The new ABC line rule on 762 isn't as good as the old one imo.
I hate it when people do it to me tho, so I typically fall back to a particular flag outside the view distance from the ABC and defend a different route. This is a game after all, and just because you're beating the crap out of the other team, doesn't mean it's fun to just keep beating the crap of them. I like to give them a fighting chance sometimes.