Kicking people because they have different opinions is exactly what we should avoid. We should only ban people if they are not cooperating in making lemmy a better place but labeling certain groups of people as “bad” and banning them while they were only expressing their dissent is not ok.
We probably wouldn’t even have to create our own lemmy instance. We could make the lemmy client (for mobile) calculate the user’s karma by adding upvotes and downvotes and display it on the user’s profile. Web extensions for browsers would work too.