I don't think there's anything wrong with banning for skill if you're completely open about it.
Again, I speak from experience as I had to do it for a job. You have to keep the skilled players from griefing the new players, and you've to stop the new players from griefing the older ones.
Whats bad about being banned for skill anyway? It effectively says "you are good enough at the game to disrupt its enjoyment for others.". Sounds like a compliment.
Furthermore, I would only do it as a server owner/administrator. As a mere admin, you enforce the will of the owner. In essence then you should be saying "thank goodness you don't own a server".
At the end of the day you have to assess the needs of the regular players. If one guy keeps disrupting the game to the point of unplayability, then that person needs to be removed from the server. I have long been of the opinion that top tier players should be forming top tier servers so that they don't have to cope with crap marine teams, and so normal players don't have to cope with some asshat whose idea of fun is to singlehandedly destroy a game as fade.
Thankfully on LM our players are mortal enough that this is not a problem, and when there's enough regs on its impossible for any one player to imbalance the game. I am discussing hypotheticals. Banning for disruptive skill is completely legit. I would ban someone from disrupting a game for being too good, and also for being terrible.
As an addendum, I would ban as a last resort. When there's enough regs on, most servers can handle most skilled players by weight of number. So generally if it was all nubs, I'd kick the skill guy and tell him to come back later. If he persists in laming it with nubs, then he'd get banned for disruption. Hey, my server, my rules.
People should be actively measuring their own skill against the other players. If you're thrashing them all and not dying in return, then chances are you're being a llama. Most players will recognise this and use pub games for practising other classes/roles, tinkering with upgrades, or unwinding a little after a game.
There does however remain a small hard core of people who play clan standard game after game, regardless of opponent skill. If it disrupted regular play then its effectively disrupting other players enjoyment, and comes under llama behaviour.
I wouldn't play my tabletop games against a kid because I'm pretty good at what I do. I got banned from playing tabletop games using a certain race at my local store PURELY BECAUSE noone could beat me when I used that race. Ever. Even if they used that race against me. At first I thought it was unfair, and that I was being discriminated against... but when maturity kicked in I realised how unfair it was on the people I was thrashing. I was teaching them nothing, and they were only getting annoyed with me.
So I kept to playing skilled players, and whenever I was in the store I'd experiment with a new race or unit. I was happy, the store was happy, and the other players were happy.
Same thing for servers. If someone's being an asshat, you have to crack down on them. As long as you're open and honest about the reasons for it, there should be no stigma.
