He has a tendency to say things and never explain why he said them or explain himself:

Today, I started clearing out my hard-drive because I had a bunch of old programs or games I don't use/play/etc. And ran across a bunch of duplicate files (Microsoft Redistributables). Thinking I didn't need ones from 2005, I started uninstalling them, only to have my brother flip at me, saying I was going to mess up my computer. I stopped and asked him why I needed that many versions of the same program.

He failed to respond and just threw his hands up going on about how "If you want to screw up your computer, go ahead!" I eventually had to do the research myself and found out WHY my computer had so many copies of the same program, and reclaimed some of the older copies. Of course, my brother could've just told me when I asked. But he never explained, never gave a reason, nothing. He just threw up his hands and acted like "Whatever".

And he wonders why people don't always go to him for computer advice in this family. He expects that we should just take him at face value when he won't even help us understand why he should or shouldn't do something. It's not enough to just tell us what we should do, he needs to at least try and make it so we know WHY. Luckily, I managed to solve this problem on my own, but to be honest this was patently ridiculous in the first place.