I don't know anything about the HSUS, but it is important that people do not confuse this organization with the many fine local Humane Societies. My local Humane Society (I believe they call themselves the "Mid-Valley Humane society") is a great organization.
Years ago I had a male Iguana that I rescued from an unheated, unlighted 40 gallon tank in a teacher's classroom. The iguana thrived and grew like a weed. Unfortunately, he had an extreme hatred of cats (we had four indoor cats at the time) and would thrash about violently whenever he saw one. After a while I decided I needed to re-home Lizzy (thought "she" was female at first...) and I contacted the Humane Society. They put me in contact with a lady who was running a reptile rescue out of her home. They were very "pro-herp", but didn't have the resources to care for a five-foot male Iguana and that's why they referred me to someone that could and did help.
Again, I can't say anything about the HSUS, but I fully support my local chapter and encourage others to do the same.