Alright fine, I'll be more specific.
If you argue for completely asinine opinions that you arrived at prior to gathering any substantial amount of objective data, and then support those opinions exclusively with information gleaned from biased sources that only seek to affirm those same opinions, then you are probably stupid and annoy me.
If you speak in cliché generalizations or platitudes as your only means of backing up whatever arguments you have to make, and those arguments are generally little more than the echoing of idiotic stereotypes, then you are probably stupid and annoy me.
If you always vote for the same political party, angrily debate political issues online using party talking points and other completely one-sided information, cannot see the middleground in anything, feel that centrism/moderation/bipartisanism is a weakness or a bad thing, and immediately hate anybody identified with the opposing party before knowing anything at all about their ideas, you are probably stupid and annoy me.
If you believe anything you see on youtube, you are probably stupid and annoy me.
If you try to pick fights on the internet for no good reason, or to impress internet "females" you don't even know and will never have sex with, or to prove what an awesome person you are, you are probably stupid and annoy me.
If you miss the inherent joke in my handle and assume it's egoism and not irony before (or worse, after) reading any of my posts, you are probably stupid and annoy me.
If you are racist, homophobic, ethnocentric, or otherwise just plain ignorant, you are probably stupid and annoy me.
and then of course there are the people who just simply are not that bright, who take offense at the wrong things, who laugh when they shouldn't and stare blankly when they should, who think I'm being condescending or disrepsectful because I used a word they don't understand. In general they're not as annoying as any of the above, but still...
and Lex is right, not all opinions are equal or deserving of respect.