There are definitely "real" dogmatic sedes, i.e., people who think membership in the Catholic Church depends on being "non-una-cum." And that's just ridiculous. Note that there are dogmatic sedeplenists too, and they're just as bad, and definitely more proliferate.
But what I think is usually the case, and what I think is happening usually when someone is accused of being a "dogmatic" sede is that the person making the accusation finds the argument strong, but if they've already "decided" that it's wrong, they need to explain why they are compelled by it. That's when the old "you can't force your opinion on me" canard gets toted out. In principle it's not all that different from a liberal, atheist, or other secular type being presented with strong arguments against their position just curling up in the intellectual fetal position and covering their ears by accusing their interlocutor of "forcing" or "imposing" their opinion on them. As soon as that card gets played, you know the discussion is over. It's basically a self-destruct button that indicates the end of meaningful discourse about the issue.
It's a poor state of affairs when good arguments-- which our minds are literally designed to accept-- are miscategorized as tyrannical impositions of opinion.