My take on this.
There are plenty of people/organizations I disagree with. For example, the Ruth Institute in Calif takes the position that hetero couples make better adoptive couples than gay couples. There is no data to support that and I think they are FOS. Are they a hate group and should they be labelled as such? I don't think so. Should they be canceled? Nope. Rather others, should debate their beliefs and let the public decide.
The SPLC thinks they are a hate group. They are using "labeling" to raise massive amounts of money. On the other hand, if they had two categories of folks: 1. legitimate hate groups. 2. groups whose opinions they don't agree with I'd have more sympathy for their cause.