More the last two reasons than the first. If you're asking why we are so concerned about it I can provide an answer for my personal reasons. There is a trend among gamers where people who do not fit the "group mind" are kicked out of groups. People defend it ususally by desparaging the style of play of the banished player. It's symptomatic of a lerger problem with the Gameosphere. That is the idea that some styles of play are "bad" while others are "proper". I can see wanting to play in a specific style and why someone playing in an oposing style could be troublesome. However, you can aleays talk to the player or (gasp) try to modifiy your style. Gamin is an intensely social personality driven activity. Try as you might to pretend it doesn't matter and you have no connection to the other people around the table, you do. Whether or not you want to.
So if everyone was playing pirates and some guy comes in and wants to play ninjas, they're all supposed to start wearing black and cut their parrots' vocal cords?
The more I think about it and read these responses, I think the better analogy for people you game with is that they are like people you work with. The big thing I'm going to talk about in the episode (or may do one just on this) is problem solving and setting friendship aside to deal with the problem. That is much more similar to the way you would problem solve with a co-worker or subordinate. The whole point is to keep it impersonal and rational and to just have it based on friendship is actually probably poor advice.
This is... a strange way of putting it. I have a very mixed gaming group. Some of these guys are like brothers to me, but this one guy is kind of annoying, like the strange guy nobody likes at the office. I love most of these guys, but I sometimes hate gaming with some of them. It's a strange thing, let me demonstrate in chart:
Person A: Good friend, sometimes gets me mad.
Person B: Like a brother, but gets me mad quite often.
Person C: Friend, but he has a way of making people laugh.
Person D: Good friend, sometimes disappears into the background, but generally a great guy.
Person E: Annoying guy, sucks at game
I have a very mixed group as you can see. You can't treat every player the same way, just like you can't treat every relationship the same way. If you have to go take off at a hangout, your buddies will understand, but you can't just leave your girlfriend in the middle of a date. Sometimes the same problem will require a different solution depending on the player.
And I am totally fine with kicking someone out, but that's usually because I, as a person, want to sever that relationship. I wouldn't want to kick out a friend who just annoyed me while gaming. I'd want to work with them and find out the problem. For instance, I get mad at persons A and B far more often than I get mad at person E, but I'd much sooner kick out person E because he's kind of a jerk.