They don't. The only preachers you are aware of are probably the ones you've seen on the media who say such things. Ofcourse, the preachers who preach good things won't make it on the media because theres no reason for it. When Muslim clerics sit there and preach ''we should be kind to people, we should respect our parents, we should practice forgiveness'' etc etc etc, there isn't any reason for them to attract publicity because this is what most people preach and it's nothing out of the ordinary. The sheikh at my local mosque has never preached anything like raping is ok or whatever, he has continuously condemned such things. He preaches goodness and tolerance and all that kind of stuff.
I am a Muslim who doesn't think in that way and if you like, I can introduce you to over a hundred other Muslims who don't think this way - and that's just from sydney.