At the end of the day enforcing guidelines involves telling people "sorry, this is not the kind of question we want here," and people are always going to find this less than welcoming -- justifiably so, since they've objectively been excluded. You can be as nice as you want about it, and I'm not advocating being rude or cruel, but it doesn't matter.
Right, I think so too. My point is more that moderation doesn’t imply being unwelcoming, and they are more or less distinct. A great example is HN, it’s a pretty welcoming place with good moderation, albeit at a much smaller size than SO.