Well to say the least, all of them are being put in bad lights kinda. I mean, Poison Pokémon are always being seen as evil, and I can see a point in that, but for some reason they always end up on Team Rocket's teams, where they are just destined to lose every single battle, so they are kinda being shown as weak too.
Once they show them outside of Team Rockets team, it's usually something tame, like with Trubbish and the playground in the B/W anime.
So yeah, I think they're being portrayed pretty badly.
This. It is either being too evil or being too cute. The badassery of these poison types are always... absent. I mean, let's look at some badass Poison types. Nidoking. Used by Gary and it easily went down. Zubat family. Used by every freaking rocket. Roserade. Where is she anyway? On drew's team? They are all gone.