Why is SPLC a hate group?

They attack or malign an entire group of people, namely theists who believe that homosexuality is a sin.
They are an organized group that hosts meetings, have a website and engage in other activities that are clearly not the work of a single individual.
Engaging in violence is not a prerequisite to be listed as a hate group.

I hate broccoli. If I set up a website encouraging people to boycott farmers who grow broccoli and stores that sell broccoli and I was able to recruit a large following, Broccoli Sux would qualify as a hate group according to SPLC’s definition. The point is, the First Amendment still applies. Nobody is forcing people to participate in “conversion” or “reparative” therapy. Be gay, but don’t label groups who disapprove as ”hate groups” because they disagree with you.

And for the record, Broccoli Sux.