First off, it’s totally normal. We’ve gone through the same and even now we get a spicy question here and there. Moderation of questions really helped us.
Hi Frederica & Tom
Moderation worked for us for a while but people got a little annoyed that their questions were being “reviewed” and monitored :(
We also experimented with downvotes and let employees decide on which questions were relevant and which ones were rude. People joked about it at first but after a quick explanation that we are really giving THEM the power to “moderate” the Q&A and decide which questions were important, we could see the rude questions going way down!
I was also thinking about using the private replies to the authors of rude questions but with the amount of questions we get at our allhands, I’d need an extra person to handle just that. Did anyone try this?
Same here 
We also tried the moderation, but there was quite a drop in the number of questions
… so we went fully transparent again BUT set some rules at the beginning like post only questions and comments that are in line with our values and you’d say to someone’s face or under your name. It helped.
I’d be also interested in the private replies. Anyone?