Again, they can do it to all users or they can do it to some users, and if they are going to do it to some users then they want to pick out some group that would make more sense than another group. A congested cell becomes less congested even if only a group of people is throttled and not everyone, so there's still network optimization that happens, which simply can't be denied (sure, it can be even more optimized but at more inconvenience to more users essentially). All of this was discussed a few times in previous replies.
Certainly people in that group aren't going to like it, and they will just call it whatever they want to call it (greed, etc.), but it doesn't mean that there isn't something more behind it all.
There is something behind it, no more than money. If it were about network congestion, then any user over a certain amount, on a congested tower, would be throttled. That would give any user that doesn't use X amount of data, a better experience.