Tethering puts more demand on the network. The more demand on the network, the more infrastructure is required to provide useable throughput to all users. This whole notion of throttling is to protect the bottom 95% of data users from those using it suspiciously.
If you hate verizon so much, why stay? With so many carriers, I'm sure you'd have no problem finding one that will please you. Well, not really sure but you know what I'm saying!