DS2 (9) asked me why we never seem to have classmate X over to play and I answered him quite honestly - "because he is rude to me, doesn't do things I ask (like take muddy shoes off in house) and is nasty to you about your toys and the things you do"
The bit I didn't say to DS is that I also think he is a bad influence on him, because DS copies his way of talking an attitude 
Out of DS1(11)'s 'friends' I'm least keen on a child who comes to our house and proceeds to turn it upside down - nosing in drawers/ fiddling with stuff (models, toys, techo things) until he breaks them, and also has no respect for our home - jumps around on sofas/beds, and goudged a big scratch in our kitchen table with a paper clip
.
In both cases the parents think their children are little darlings/angels. I wish I had the guts to be honest with them...
In the case of the table incident, I DID mention it and the mother just looked a bit crestfallen, and said, "Oh poor Y, I expect he didn't realise he was doing it..."
No apology or anything....