Canada

For what it's worth, I don't do that -- at least not deliberately. I think we all tend to be a little less vigilant about scrutinizing information that confirms our biases; It's a natural human failing worth first inward attention and second consideration when accused of it. I actively guard against it, but cannot guarantee I never slip.

It's also super tiresome when people discover it's a magic trick to disingenuously waste thoughtful people's time. That's a tactic employed very unequally across the political spectrum.

More to your specific concern, I very much dislike political ads not endorsed by the party they support, especially if they're deliberately obscuring their motives. Messages from unions tend to be motivated by values that align with mine, which makes it all the more frustrating when they employ the very tactics people like me spot as discrediting. It's like having the truth on your side but instead lying or misrepresenting facts just to take a more extreme position -- and all it does is abandon the high ground and strengthen the resolve of dissenting views.

You can't reach reasonable people with unreasonable tactics, and you can't reach unreasonable people period. The latter are going to blindly accept or invent whatever empowers their motivated reasoning. Until you have the power to change their motives, it's a lost cause.