In my youth I never had to worry about having to ask anyone to leave a game I was running. Everyone that ended up in my games was a person that I interacted with socially to begin with. The few times that tempers flared or something went wrong, it generally wasn't much different than if I had a disagreement with that person over a video game or how much pizza they had eaten at a party. In other words, it was just another form of social interaction with a person that was already within my social circle.
Far further into my adulthood . . . so much further that I may soon officially and literally be a grey beard, I find that life has changed a bit. For years I have been gaming with people that I have met expressly to game with, and these days I run all of my games in the public venue of the FLGS.
That means I get a wide range of people showing interest in my games. It is actually very enlightening and it has actually broadened my horizons as a gamer quite a bit. Casting a wider net brings in more diverse groups, which in turn means that you can never really be sure what someone is going to do until you get to know them better. Also, getting to know more people in life is generally a positive thing.
That having been said, in adulthood I've had to brook the topic of asking people to leave my campaigns, which is something I had never done before this phase of my life. It is very, very hard.
Unless I'm mistaken, I've only had issues like this three times thus far, and I'd be happy to never have to deal with these issues again. The first time really wasn't all that traumatic. The gamer in question was very busy with school and work and had missed a ton of sessions in a row, and never managed to catch up on what was going on. When his character did something, it tended to get the party into trouble, and without the familiarity built up from having a regularly interacting group, this tended to not play well at the table.
In the end, I talked it over with him, and he agreed that he didn't have the time to devote to a game, even one that occurred every other week, and after I asked if his attendance would be getting any better, he agreed that he should open up the slot.
Wow, that wasn't too bad. Everyone was an adult, we still joked around on social messaging sites and the few times I managed to see him at the game store before he left. Hey, adulthood isn't so hard now, is it?
The next time I asked someone to leave the campaign was . . . complicated. I had a player that just up and left the area for a few weeks without really talking to anyone at the store or that we knew in common. As far as anyone knew, he wasn't coming back, and when I finally e-mailed him, he took a while to respond.
I opened up the slot in the campaign, got a new player, and then received a response from the player. He told me he would be back in two weeks, and I told him I had already filled the slot in the campaign. I then told him that I wasn't planning on expanding the group to let him return, because I didn't know if he was going to leave again without notice for weeks at a time.
What surprised me about this instance was that the player in question then threw the first player I mentioned back at me. He pointed out that, in aggregate, he had missed more sessions but I waited longer to ask him to open up the spot in the game.
I was on the defensive, and I felt bad. It was true, the other player had missed more sessions. But I knew the situation was different, at least in a way that was important to me. The difference being that the first player that I mentioned had been e-mailing me, if not before the session then during the session, telling me that work had run over and that he was sorry and telling me he was still interested in the campaign. In the case of the second player, there was no warning, no discussion of how long the player would be gone, or even a reason given.
No player owes me an explanation of their personal time, but if I don't know why you aren't showing up, then all I know is that you aren't showing up.
I have had other players that have had extended periods of leaving the campaign, and they were great at communicating when they would be gone and giving me a good idea of when they would be back. I have no problem with that. But the lack of communication and the assumption that I'll always be flexible without the courtesy of a warning did take me aback.
That brings me to the last few weeks. I won't go into too many details, but my session two weeks ago ground to a halt in a way I have never experienced before. Essentially, I was taken off guard because the player was arguing with a decision I made for an NPC and for the campaign in general directly to me, the person that is the GM, not to the NPC, and was refusing, as a player, to keep playing until I changed the scenario.
When we took a break, refocused, and got going again, I noticed that the player in question was not participating at all, nor was he communicating or even showing any sign that he was enjoying himself. I had a very hard time getting into running the game knowing that someone was having such difficulty with my GMing style.
I decided after a few days that I needed to put my cards on the table and just tell the player in question that I didn't think I was going to be able to run an enjoyable game for him, and that I thought it was best to open up the slot for a player that might be more in line with my GMing style. I got no response, but the player in question did not come to the latest game session.
The long and the short of it is that none of these situations were entered into lightly. We are all gamers. I'm no better than anyone else, and I'm certainly not perfect. I run games because I have fun doing it, and because I am rewarded when I see players enjoying themselves. That really is the crux of it. If someone is either not getting anything out of the game, to the point of being angry, or they are doing something that throws me completely off of my ability to GM, the group has a problem.
If I can't GM well, that is five other people at the table that are wasting their time when they could be pursuing other hobbies or playing in other games. I'm sure there are better GMs that could either shut out the mental noise or figure out how to make the "odd man out" enjoy the game more, but I'm not that guy, and I wish I was.