If Sky pays money monthly for his server, he can do whatever he wants with his server. If he doesn't want people to use scripts on his server, people should respect that wish. If people don't, he does have the right to ban them.
The fact of the matter is, scripts do give you an advantage. I will admit that not all scripts give you an advantage and not all scripts should be a bannable offense, but there are some scripts that people should not be allowed to use. The swoop script is a perfect example. The teleport script from 1.1 was an even better example.
edit: I just want to add one more thing. While I do believe he should ban people he knows uses scripts, I don't think he should go around banning everyone he suspects of using scripts. He should have proof that they do infact use scripts (IE: The person admits it or he gets a plugin that tells if people use scripts)
The fact of the matter is, scripts do give you an advantage. I will admit that not all scripts give you an advantage and not all scripts should be a bannable offense, but there are some scripts that people should not be allowed to use. The swoop script is a perfect example. The teleport script from 1.1 was an even better example.
edit: I just want to add one more thing. While I do believe he should ban people he knows uses scripts, I don't think he should go around banning everyone he suspects of using scripts. He should have proof that they do infact use scripts (IE: The person admits it or he gets a plugin that tells if people use scripts)