Clearly those who are advocating "throwing kids off the team" have probably been down the path where there is so much disorder that there really isn't any other choice; or they've stepped into a situation which requires control. I doubt (for the measley amount of money coaching gets) that most coaches are in it for the power trip.
When I began coaching I was cautioned by a very good and well respected coach (mentor) to not make too many rules, or you'd have to start abiding by them...too much black and white. Gray areas actually help you individualize the issue and get help where necessary.
But in some situations; and some locations; I can see where a coach needs to come and be the heavy. Without knowing the details of the situation, we can't make an accurate assessment.
I had a kid come out my first year as a coach. He showed up the first day, and then I didn't see him for two weeks. His dad showed up at practice one day to see "Johnny" do a workout, because "Johnny" had told him he was one of the varsity guys.
"Johnny" wasn't there - he had duped his dad; and was going to a friend's house to smoke weed and hang out. His dad came back to me asking if he could "make it up." I told him that there would be a spot on the team (he was an ok runner, generally good kid - not a varsity runner) as long as he didn't have any unexcused absences or any behavior issues - especially relating to drugs or alcohol.
So, I made an individual rule based on the kid's circumstances with direct communication to the parent. Never had a problem with "Johnny" after that. His dad even sent me a gift certificate to a running store after "Johnny" graduated.