Not all Slytherins are abused, but I rhink it's more likely the children of the Death Eaters are abused.  Crabbe is scared of his father, because he got into trouble at school for doing something to his Head of House, which is a really bad thing according to how I see the Death Eater mentality.  The parents would be angry and suspicious of Snape if he were punishing their kids for something they did to another student--say a Gryffindor--but this was an attack upon their Head another Slytherin--which is NOT a good thing.  I see Death Eaters as a cross between a terrorist cell, nazis, and the Mafia.  You don't attack your own , espcially not your leader, which is what they did==they stole from Severus, invaded his privacy, and harmed his familiar.  So I would say they are in HUGE trouble with their parents and they have a right to be scared.

Like I said before, not all Slytherins are abused, nor do I think all the teachers hate them.  I also disagree with the notion that all Slytherins are evil.  That's just not realistic.  In canon we always get to see the nasty ones, but there's more than just those few in that House.  And you can't say that 1/4th of the student body is bad.  Ambition is not a bad trait to have, half the world leaders have it and so do many successful people and that is not evil.  But it can be turned to evil, as can any trait.  Intelligence used the wrong way can be evil, so can loyalty to the wrong person or ideal, so can courage, if it's blind and unwavering.  The terrorists who blew up the World Trade Center were brave--suicidally crazy and brave--but they were EVIL.  I never understood why JKR had four Houses and said they were supposed to all be necessary and all needed to get along and yet never showed any Slytherins with good qualities, except Severus.  It didn't add up.  So this is my answer to that, there are good ones and bad ones--Crabbe, Severus, and a few others here I've shown to be decent representatives to balance out the ones like Malfoy and Goyle and Voldemort.  I also think there were Death Eaters from all the Houses--you just didn't hear of them, but that doesn't mean they weren't out there. Every House has dark and light, that's what I'm attempting to show here.

You'll see more interaction between Sev and Harry hawk later.