I don't mean to generalize and bash every SUV owner, but my anger is out of the majority of people I see and speak with.
The thing that REALLY irks me is the people who think that buying an SUV will make them "safe". Instead of taking the responsibility and drive safely, they buy the biggest vehicle they can find and then drive like they are invincible. Their recless actions may not cause THEM harm, but they end up causing the rest of us harm and inconvenience.
One scenario that always comes up is when it snows out. I have friends who go out (when it's dangerous out), and I'll say "I don't want to go out because it's dangerous out there" and they'll say "so we'll take the SUV"

Like this makes it safer??? Sure, you may get out of a ditch easier, but on icy roads, you're better off in a lower-to-the-ground vehicle that isn't as heavy. So, when there are those times where you HAVE to go out in the snow (like to the hospital or to help someone out), you have to battle all the "joy riding" SUV owners who have no fear of the dangers because of their SUV's.
The other thing is the WAY they drive. Since they feel so safe, they don't realize how much MORE hazardous their mistakes can be. A mistake is incredibly magnified by an SUV over a smaller car. I've seen it thousands of time. You just CAN'T (and shouldn't) drive an SUV like it's a "road griping" sports car, yet so many do.

Another thing is the fact that they take up way too much room (as noted in the above parking lot scenario). I was driving on a 2 lane highway and there was a Hummer in front of me. We were both in the left hand lane...when we got to some jersey barriers (and a bridge), the Hummer had to drive in the middle of the highway because he was afraid of being so close to the barriers (and the bridge) if he stayed in the lines. So needless to say, he blocked BOTH freakin lanes of traffic!

And you can't see around them, so it's so hard to navigate traffic. I hear SUV owners always saying "I like how high up I am" - Well, that;s because there are so many SUV's on the road! If there weren't so many SUV's, you wouldn't NEED to be so damn high up. You don't solve a problem by ADDING to it.

And (as Phil pointed out), it would be one thing if people used them to transport kids, but I ALWAYS see a single driver behind the wheel of these SUV's. I realize that these people probably DO have a bunch of kids and they are just driving their vehicles to work, but this is what I mean by a bad thought process. You should really only be using these things to transport your kids, they shouldn't be used as "everyday" vehicles. Kind of like driving with snow chains, on a road with no snow

. And if you can't afford to buy 2 different cars, then PLEASE rethink the SUV choice. People survived LONG before these things were invented.
And besides, how many families have more than 3 kids? Families used to be BIGGER years ago and they didn't need these SUV's. Most SUV owners only have 2 or 3 kids tops. I think it's laziness and a selfish attitude that drives them to buying these things.
p.s. Can you tell how much I DESPISE these things?

Try driving 500+ miles per week, on the worst traffic-jammed highway in the North East, for the past 10 years, and you'll see why I have this attitude.