I don't know the work of Karl Popper all that well. I do understand that he formulated the idea of falsifiability being an integral part of science, and that does seem like a positive contribution. But another concept of his has been popularized―yea and verily, it is even memetic. And not necessarily for the better.
The above graphic tends to be shared by the same general group of people who have made a fetish of Randall Munroe's "Free Speech" comic, and for similar reasons. To take whatever edge they have in debate and make it permanent, regardless of events. Illustrated thought terminating cliches, in essence.
So to examine the argument fairly, are there times when intolerant ideas must be excluded in order for civilized debate to continue? Potentially, conceivably, maybe. The problem is, who defines? How do you distinguish an intolerant idea from one you just find disagreeable? The truth is that an in-group can very easily define any serious opposition as intolerant, and thus justify themselves in destroying all those who disagree with them. Means less time debating and more time ruling. And I think a lot of that has been happening.
Then, too, how does oppression begin? A lot of us associate it with hateful men targeting the objects of their hatred and persecuting them. Certainly there have been times in history (Jawohl!) when one has accompanied the other. But a more common factor has been a group acquiring large amounts of power and then abusing it. If they are motivated by evil ideas, those often don't make themselves known until afterward.