Flexor the Mighty!
18/100 Strength!
Oof, that’s rough. I’ve been there, too. Where the one problem player has the potential to take other, decent players with them if they leave.
The way I see it, you can work to minimize whatever problem behavior is going on for the sake of those other players (that’s what I did at the time), or just directly address the problem player or outright boot them and take the possible hit. When the person’s a friend, it’s already a difficult thing to address. In an ideal world, you could tell a friend, "Hey, this behavior that you do is making my job as a DM harder, and making the game less fun for all. Please don’t do it anymore." But no matter how polite you are, they’re more likely to ignore the request or deny that they’re doing anything wrong, and/or get angry over it. It’s a no-win situation.
I've started emphasizing that they need to change their approach to this and we need to stay on point and it worked last night at least, I'll keep my fingers crossed. I run a fairly beer and pretzels game and I think things drifted a bit too far off at times.