oh yeah, its most definitely inhumane, i would never do it. but it can be done. My roosters seem to find crowing one of the funnest activities they can think of, i just wish they didn't have so much "fun" at 4 am... but it would be terrible to take that away, i'v seen videos of "de-crowed" roosters pointing their heads up and trying to crow, its kinda sad.
Surgically de-crowing a rooster is like de-barking a dog. Cruel, useless. Now, there are people I've heard who ended up with a rooster that had a "crowless" gene. As in, they never crowed. Don't know much about it though.
If you can't have a crowing bird, rehome him. If you are bothered by the crowing, you will get used to it like people do when they live next to a railroad, airport or a highway.
We used to have crowing at 4:30AM until I taped the coop window glass with a black garbage bag. Now, when we open the coop door at 8AM, they are still sleeping on the roosts.
But, you cannot stop him from crowing during the day. That's his job.