MB, I wouldn't have a small dog ever because I find IME a lot of the smaller breeds to be bad-tempered and vicious and I think they have a worse record for biting than big breeds (?? Am sure someone will have stats on this somewhere....??) - I've certainly only been bitten by small dogs despite spending my life amongst large breeds.
The whole Rottie thing though isn't fair on the poor breed - it used to be Alsations when I was growing up, but no-one says a word about them now. The unfortunate truth is that every generation there is a breed that starts to become fashionable with thugs, then all the thugs go and get one, they get overbred (the breed, not the thugs) (then again...), the dogs don't get trained properly, don't get treated properly, and start causing havoc.
No-one says a word about alsations now (or boxers - another breed that had it's 'thug' day) and that's because that now they are not popular with the hooligans they are only owned by real dog-lovers who get them from reputable sources, and train them proporly. A properly-trained and cared-for dog is unlikely to attack ever unless it is protecting a 'pack member' (it's owner) or is under severe provocation (just as I would be unlikely to kill unless I was protecting my child, in which case I think I would do so in a heartbeat).
attacking a breed because they have become popular with thugs is just not logical. What you want to do of course is stop thugs owning dangerous dogs. But that's another story altogether.