Definitely votekick and report.

Even if they were queued with one friend, if that other person agrees with the kick, the kick will go through.
And if it doesn't, they kick you and you're free from further abuse.

I have no idea if reporting people has ever resulted in anything being done to players like this, but GMs do ask for timestamps to help them look up the instance and logs relating to the incident. So if they can find it and confirm it was bad and unprovoked, maybe it goes on their record.