Some of the ads that Russian trolls purchased were for legitimate political causes.

Sometimes Russian trolls spread fabrications (fake news). It's wrong for anyone to do that.

Sometimes they support legitimate campaigns for various political positions. Even though I may support some of those campaigns myself, I object when Russia does so in a disguised manner.

These ads don't represent sincere support for any cause, not for Sanders and nor for the troll.

Likewise, I object when right-wing billionaires and fossil-fuel companies employ people to spread lies. People have the right present their views, but we don't have to allow the rich to hire sock-puppets.