People are angry for any number of reasons, some justified, some not. There are of course people that simply enjoy the unhappiness (real or imagined) they cause people to feel. Generally speaking, if you feel that someone is deliberately attempting to incite a reaction from you, it is best to simply ignore them. Personally, I restrict 'ignore author' functions for people that I feel there is absolutely no benefit in interacting with; they don't even have to be particularly abrasive.

In short, look at the source and don't just assume that every person has an axe to grind. In particular, unless people are specifically asking for advice, they don't always respond well to it. It can be very difficult to detect tone and intent without pitch and body language so your benevolent efforts to assist them could possibly be perceived as condescending or patronizing.