Sexual assault, bestiality and necrophilia are all examples of sexual behaviour with non-consenting parties.  "Consent" isn't always a bright line, either, and I think that's one of the things which disturbs people about some paraphilias - there can be enormous risk of harm if the parties involved aren't all mentally healthy or if the power dynamics are distorted.  In fact, DSM-V is trying to address this essential difference between people whose non-normative sexual behaviour is psychopathological (ie causes harm, impairment or distress) and those in which it's just a "quirk".

A lot of paraphilias have "communities" and those communities attract extremely disturbed as well as well-balanced individuals.  It's the extremely disturbed ones that you tend to hear about.  Some are predators right from the outset and some seem to progressively become more and more immersed in satisfying their particular kink until whatever has previously kept them grounded breaks down.  It's those individuals who operate at the extreme that you tend to hear about.

At an intellectual level, I think many people are aware that "if you can imagine it, someone is masturbating to it".  There are certainly some people who think "if it doesn't turn me on then it shouldn't turn anyone on", but I think that many people's reactions to the paraphilia's of others are a bit more complex than that.