Reasonable ban. People fuck up sometimes and should be kicked from a community for it. Age, mental state, irl problems etc. None are an excuse. Some attitudes don't belong in some communities. The fact it's only 5 years and isn't an irreversible perma ban is already more than reasonable imo.
Look at it from another point of view. If someone was to heavily insult a dead friend/family member, would you want to keep them around? Would you forgive them? Would you never talk to them again? What would you do?
Some other things should be considered equally awful. Like being a paedophile. However, a lot of the behaviors nonces get banned for are not for kiddy diddling, but just for sending one out of order message to a minor.
I really respect the protection that underage people are getting online from leagues now. Often they don't know any better and need the help to stay safe. But always remember, it's a ban in an online game. Not a real world punishment. The severity of a ban should be closely related to things that attack the league and players directly through the league, since that is what they control. Not based on things that happen outside the leagues power.
I know it would be nice to live in a perfect world where these behaviors are nonexistant, or the league would ban and remove all of these individuals from the community, but that is not possible without other problems. The first isn't possible, and the second would mean the league is exercising authority where it does not belong, which is equally as bad, if not worse than banning all these people permanently.