From What I Know
The Musings of a Karate Guy
Short answer; yes, twice.
I distinctly remember both of the conversations and they were tough, but necessary.
Our dojo has a code of conduct (reminder to self, review this with students periodically) which is read and signed during the enrollment process. This list of expectations is all built around the idea of protecting not just each individual student, but our class community as a whole. Protecting the spirit of and community of our group is one of my primary concerns and responsibilities. Without a strong community, learning becomes more difficult that it already is. Without being able to trust your partner(s) it's impossible to embrace the idea of taking a risk.
So yes, in order to protect the community of learning in our dojo, I have asked two students to leave in the last decade, after an unchanged pattern of behavior which which both individuals were unwilling to address from their end.