> Calling a named individual an "absolute scumbag" in this context is fine grounds as any for a lawsuit.

Based on your misunderstandings of US defamation laws, and the fact that you jumped to stabbing over shooting, it sounds like you've been steeping too much in eurotrash defamation rules. Here in America, truth and opinion are both perfect defenses against defamation lawsuits. My comment consisted only of true facts (the man donated to support prop 8), and the opinions that follow from those facts (the man is a scumbag). You can only sue someone for lying about you, and for public figures like a CEO, you need to prove they were lying on purpose.