Your State Legislator is a public person doing the publics work. Use of their name and their corrospondence in the performance of their duties is lawful. It does not break any copuright or privacy laws.
The tone of that letter suggests that they are for any new laws that will inhibit your rights. I would also say that it is a "canned" letter, sent out to anyone that is against their positions.
Seen many like them before.