Why is it a bad thing if someone you don't like says something sensible?
There's a lot of natural alliance between the anti-establishment on the right and the left... that's why the establishment spends so much money and effort making propaganda, trying to make sure that the natural rage of the screwed-over gets channeled to the far right. The rage gets aimed at the left, instead of being properly directed at the people who are screwing them.
I don't feel like it's helping if someone who's a victim of that propaganda makes a good decision, and people on the left don't want to acknowledge it.