I honestly disagree with this.
Just because you have bad rep does not mean you deserve to be banned. You deserve to be banned or warned if you have broken the rules.
I've seen a few people get banned when they've had about 200+ rep. It shouldn't be based on how much rep you have, it should be based on if you've broken the rules or not.
A person can have negative rep just because of their name or history with others, but if they have been following the rules, they shouldn't have to deal with that type of penalty.