Of course Skeptics should be 'allowed in'. What they should not be allowed is to be abusive, rude, sneering or just generally obnoxious. I've no problem with any Skeptic saying ' I don't believe a word of this...show me proof', but I do object to people who think that just casually dismissing things as a foregone conclusion is science.
Proper science is about investigating things. It is not about deciding in advance that this or that is 'impossible' but about looking at the evidence. Some claims DO have little or no evidence, and for those one should be highly doubtful. But what I cannot stand is those who just come onto forums with an a priori mentality that 'its all rubbish...the whole lot of it' and are not even prepared to listen to or consider any counter argument.