As far as Binky is concerned, I always assumed it was simply a case of character development. He really didn't start becoming one of the guys until like Season Two or so, but even then, the dynamics were ambiguous, because a lot of the kids still had a fear of him, or still regarded him as a bully. Again, it's one of my theories as to why we rarely see the older episodes anymore, because it might confuse kids to see Binky as a bully in one episode, then a friend in another.

As for the other Tough Customers, you have to remember, Binky "de-founded" them in "Arthur's Big Hit", so it's possible that because they no longer had their club, they no longer had anything to do, and that may have softened them up, I don't know... but in this day and age with people taking anti-bullying views and ideals more seriously than ever before, I doubt the Tough Customers would really have a purpose to serve on the show anymore. If anything, they would probably have a "special" episode dedicated to bullying, but with a new one-shot/guest character as the bully.