Rebuttal:

Each time we increase the speed limits, people begin driving X mph faster than what's posted. If speed limits were 125, we'd all exceed those limits eventually.

While I think the first half of your statement is demonstrably true right now, I think it has more to do with the fact that speed limits are unrealistically low than because people will always exceed the speed limit. I believe that Interstate highways can realistically be driven at 90MPH. Assume that's the case for a second. Now assume that people want to find the natural speed of a road. If the speed limit is 55MPH and they feel that they can safely go 15MPH over, then they're going to drive at 70MPH. If the spped limit's 65, then they're going to drive at 80. But if the speed limit's 90, then they're going to drive at 90, because that's the right speed. This is assumption, to some extent, but it's based on a small personal sampling of traffic patterns in my experience.

Most drivers on the road are mouth breathing knuckle-draggers, and honestly, I don't trust them to drive over 65-75 mph safely.

Good point. Perhaps we should have driver ratings, so that some can go only 55, some 65, some 75, etc. There could be other restrictions as well, like lane restrictions. Of course, the rating would have to be obvious to other drivers, especially cops, and that's a problem because I might be driving my grandmother's car, and while I have a 1-A rating, she may have a 4-F. SO this might not really be feasible, but it would be ideal, I think. Regardless, good point.

Recently, we did increase the speed limits.

That's not much of an argument.

The current speed limits are a compromise, taking into account the fact that we know people exceed them.

Repeat; already rebutted.

The faster we drive, the more alert we need to be.

Making one thing illegal because it might possibly lead to something else is one of my biggest pet peeves. Make the wrong thing illegal, not the thing with which it combines. Of course, you could conceivably argue that the speed is more wrong than the distraction, but I wouldn't agree.

To avoid a speeding ticket, one needs to be an alert driver

Basically, drivers suck, and making them hyper-aware due to fear makes them suck less. Okay. There's something to be said for that. But there are horrible drivers that can cause just as many accidents who drive exactly the speed limit. My mom is one of them. Speed is only one of the potential problems bad drivers exhibit, and it's probably not the worst. Wild lane changing is likely to be much more dangerous.

I can speed if I'm being alert enough

So an ad-hoc ratings system.

Basically, we mostly don't disagree on the issues, but we come to different conclusions from them. You seem to be interested in going faster than other people. It kind of comes across as elitist, although I'm sure that's not what you mean. On the other hand, I'll readily admit to being elitist.

I don't think speed kills. I think bad driving does, and that's what needs to be outlawed, not speed. It's too bad that Darwinism doesn't work here, as one screwup can take out more than just one bad driver.