People who use profanity and personal insults tend to heavily degrade the quality of a forum. And when banned, they react angrily and make alternate accounts again and again.

A shadowban reduces the incentive to dodge bans via new usernames. Reddit mods don’t have Ip address access or other tools, so shadowbans are a necessary tool.

You weren’t banned for speaking contrary to the mainstream. You were banned for insults and personal attacks, indicating you weren’t likely to lead to productive conversations.