I would have said: We give them chances to curb their behaviour, if they dont change we remove them.
Giving people 'changes' to curb their behaviour might not be too productive, and removing them after said 'changes' seems rather onesided if you dont give people a chance to stick around
There is a step before removing users - the moderation queue. That's where all posts need to be approved by a moderator before the public can read them. The moderation queue has been very useful at keeping people who can't be calm and polite from spreading their garbage here, while their useful posts are read.
Spammers, however, go straight to the account removal.