I feel like the kinds of people who assume every pepe is a symbol of hate are very similar to the kinds of people who assume that all metalheads are satanic. Some are, and some aren't. It's an overly reductionist view.
Man, I love frogs. The alt-right can't take Pepe away from us.
If you look at the same section of the ADL website that Pepe is in, you'll see the first page is just full of simple numbers (symbols are listed alphabetically). I don't see anyone doing a similar study to the one posted here, but with "100%" instead of Pepe.
Also, side note, ADL lists "ACAB" as a hate symbol because some skinheads are racist and use the phrase. They have a similar disclaimer in the Pepe listing that context is an important consideration.