SPLC is not a hate group. It provides valuable information to the public about what groups and organizations are about so that people can make informed decisions about whom to deal with or believe. Forewarned is forearmed.
A friend of mine went to a new church with her then-teenage daughter, who was going through teenage troubles, sometime in the 1990s. Only after the service began did they realize that it was a hate church, but she was able to get her daughter out of there fast. Neither of them are LGBT, but if they were? SPLC's warnings are very helpful in this sort of a situation. A lot of these groups have innocent-sounding names, but actively recruit and/or solicit donations, and it can be difficult for the average person to navigate this landscape.
When I was a kid, the designation "church" indicated that it was okay, but nowadays one has to ask "what church," "what denomination."