I don't know much about the methods they used, but the results are hard to argue with.
I'm highly skeptical of the guilty by association nature of what they've done, but I think there's also some room for that sort of thing in specific situations. MS13 members don't exactly hide their affiliation.
Like anything else, there's a lot of slippery slope when trying to pass blanket legislation to deal with a nuanced problem. From what I've seen it looks like they took some common sense steps to deal with the problem without replacing them with a state sponsored police state that's just as bad. But I haven't really looked into it beyond the surface level.