How many people were jailed or disappeared for their dissent?
Being able to dissent doesn't mean that people accept your opinion, it means that you are allowed to make your point using your own means.
People still get to disagree with you, point out where you are dishonest or mistaken, etc. etc. etc.
The idea that dissent wasn't tolerated is absolute BS. It was tolerated far more than it should have been, far more accommodations were made than necessary, such as in the military, which injects people with all sorts of vaccines but somehow decided that this well-tested one didn't have to be because some people were scared.