I agree that at least some of it looks like crabgrass, though I'm not
sure it's all crabgrass. There may be some other weed type grass there
as well. Af riend of mine has a rough blade type grass growing here in
NJ that goes from brown to green this time of year. And whatever it
is, it's not crabgrass.
I agree with Jim, if you kill it now, it will look bad for a few weeks
as the crabgrass dies. The optimum time to kill any crabgrass that
escaped pre-emergent treatment was a few weeks ago, when the plants
were still small and easier to kill.
On the other hand, leaving it there, it will continue to grow, still
look pretty bad and choke out desirable grass until first frost. So,
it's a mixed bag as to what to do.
Acclaim is effective and what I use, but at this point you will need 2
treatments to kill it. Also, don't apply any herbicide when it 85+ out
or the grass is stressed from lack of water.