Sampling is a tool used by musicians, in my opinion. Relying too heavily on sampling is the sign of a hack but could you imagine all those early 90s hip-hop tracks WITHOUT Dr. Dre on the wheels of steel? Turntablism is a musical performing art, in my opinion, even if it does involve borrowing other people's beats.
Samplings been around as long as hip hop, it's almost like something if you're a producer its something you should totally be capable of doing IMO, and do it well.
Personally I love it when a producer takes the best of both worlds, putting synths & keys over samples, stuff sounds amazing!
As someone whos seen the creative process and have done it before when it comes to producing a track, and I think Dunce and Zeb can say amen to it, its a process making beats, but there are points in the process where stuff just flows out of your head and its almost a high you get when it happens.
I don't do it much now, partly because i don't know why, I get angry when I try now because I'm forcing stuff. But when I was heavy into it, nothing was a better feeling than hitting that zone.
But people can say that hip hop producers aren't musicians, but I'd beg to differ. If anyone has seen guys like Black Milk or Hi-Tek at work (and you can, check out youtube) you'd see theres more than just playing around with noises.