There are two parties that decide what constitutes an intelligent, well-reasoned critique.
The first party is the owner(s) of a platform. For any owner, there is incentive to preserve power, but there is also incentive to not act as an oppressive villain.
The owner sometimes has ideals beyond power, such as cultivating free communication to build ideas for a better world.
But even the most callous, iron-fisted dictator can sniff the danger in being overly oppressive. They also sometimes recognize that unstifled communication serves as a competitive advantage.
As a consequence, free speech is less fragile than it seems. There are even whiffs of it in China itself:
https://www.cecc.gov/freedom-of-expression-in-china-a-privil...
The second party that decides what constitutes an intelligent, well-reasoned critique are the viewers of and contributors to a platform.
We have pitchforks, and pitchforks have sharp ends, but they can be dulled by overuse. Furthermore, the citizen's militia grows weary when called upon too often.
And thus, when the rallying cry is sounded for the non-event of a crude slur being censored, we're eroding our own power. We're jumping the gun, which should fire only when we think an intelligent, well-reasoned critique has been suppressed.
Making a slippery slope argument is betraying a lack of understanding about the above complex dynamic.