Is something a "toxic" viewpoint when it's holders take action that is harmful? Certainly that's why racism is bad, but what about more controversial opinions? People who spread the belief that abortion is OK are encouraging more people to get abortions, which the pro-life movement equates to murder (and therefore harm). What about meat consumption? Vegans and PETA-types would label this harmful as it involves the death of animals. What about weed? LGBT normalization?
This labeling of speech as being "harmful" is necessarily subjective. What happens when operators of major discussion platforms decide that things besides racism are too "harmful" to permit discussion of? Seeing that limiting the discussion of ideas shapes how a population propagates them (taking this study's claim at face value), do we really want to normalize this sort of censorship? Is it even moral for site operators to manipulate people's perception of reality like this by censoring what they see to shape a population to be politically homogeneous to the operator's views?