Can someone explain the bad side of the Humane Society of the US?

As someone who once supported PETA until I learned the true nature of their organization, I was intrigued today when I found several groups that oppose the Humane Society of the United States. I thought that the HSUS was a legitimate organization who truly fought for the rights of animals.

Can someone briefly outline to me in layman’s terms the most damning things that the HSUS does or stand for that shows it’s lack of care for animal rights?