I don't get it

I don't get why having new people here is a bad thing. Don't you think that things would be better if the majority of people in the U.S. and Canada, U.K., Australia, among other places like France,
Sweden, Germany etc. were 4channers?

No, because not everyone is cut out to be an Anonymous. 4chan can help mould people already on the path to Anonymous-hood, but it's unlikely to change the common man into a /b/tard.

More people on 4chan will change 4chan itself rather than changing the people. If we go mainstream, we will be dumbing down and losing all the lulz.