[pavas]

You're talking about the dog not minding being in the crate since you've taught them its nice and cozy. In that case why does it have to be a crate, why not say, an indoor doghouse?

As far as that goes, there's nothing wrong with that and that's not the part that people actually have problems with (but it's a nice strawman to argue against).

The part that is cruel and abusive is locking them up when nobody is at home so they can't damage your possessions. If there is some emergency like a fire, intruder, something falling down, etc, they can't do anything about it.