You understand the steps. The first step is giving them a warning that what they are doing on your forum is unacceptable and that they should stop. When they continue to act in the same manner, then you have no other options than to ban them from your forum. I don't even understand why some forum members will be dramatic though.
The way I run my community is that whenever it is very obvious that some members are openly having disregard for the community rules and regulation after giving them several warning and trying to remind them of the rules they should observe whenever they are making use of my service but they decide to still continue what they are doing, I will be left with no choice than to excommunicate and ban them from the community.