Why are people such jerks sometimes?

I was asking a question about cars, this guy who doesn't know what im talking about but thinks he knows insults me and doesn't answer my question. I knew exactly what I was talking about, but he thinks I know nothing cuz hes never even heard what ive been talking about so he makes so dumb comment like I think your just joking but for the heck of it ill just play along(main idea of what he said). WHY do people screw around on here so much? Im basically just venting right now idc insult me. Blahhh people annoy me sometimes..