Originally Posted by ShesNoGood

well ... we know where he got that from from. in the book it is says-
"..., for they had been most unpopular. Elderly Mr. and Mrs. Riddle had been rich, snobbish, and rude, and their grown up son, Tom, had been, if anything, worse."
and ofcoarse... he is also hier of Slytherin whom hates muggles himself. So all Tom needed was a reason to kill (his father leaving his mother) and it was done.