Whilst I agree that the comment you refer to is absolutely abhorrent and should be treated as such, I also strongly believe that people have the capacity to change and that we as a society should be pushing for that change.
If that comment was from a number of years ago, any number of things could have happened to change that persons view of the world and the people in it.
If you have someone who's so misinformed that they hold these horrendous views then casting them aside forever is, in my view, the opposite of what we should be doing.
In the physical world we tend to put people in to the 'correctional' system (whether it works as a correctional system is very much up for debate), but in the virtual world, we just censor them and let them go away and reinforce their views with each other in their own space.
We'll never get a better society if we don't challenge the nasty parts of it and work out why people go down that path and, critically, forgive them if they change.
Also, that comment is interesting because the actual things stated (higher violence, worse economic output, net burden on the state) are literally true and uncontroversial but the way they are phrased and the mere fact they are brought up at all tells an unpleasant story.
Unless of course the commentator is just ignorant or uncaring about such implications (e.g. an edgelord).
The comment in question was posted on /r/allmyopinions.
Eh, depends on the comment. I recently saw a particularly erroneous comment about COVID-19, so I checked the poster's comment history to see whether it was worth trying to engage them in good faith, or just post a dry correction for others to see. I then saw this comment posted earlier that day:
> I don’t know if it’s blacks in general that are just retarded or if it’s balcks coupled with the history of slavery that makes them so useless and violent, either way I think this country would be VASTLY better off without them.
...I think it's pretty fair to label them based off of that one comment. For content that abhorrent, any number of occurrences above zero is enough to tell what kind of person a user is.