If you have a problem with a member and nothing against the rules is occurring, you can choose to ignore/block the person in game, in the chat, and on the forum. This is the best option if you have a problem with a person. This will prevent them from contacting you and escalating the situation. You have to ignore them in all three areas, so if you only want to ignore them in the forum (for example), that is possible, as well.
If a rule is being broken, alert a mod. DO NOT POST IT IN THE PUBLIC FORUM. Attacking or negatively discussing any WP members, whether or not you name them specifically, is against the rules and can result in infractions. If you earn enough infractions, you will receive a temporary automatic ban.
Remember that in a public forum, there are going to be many different personalities. Some you will get along with, others you will not. That is the way that life works. How a person comes across to you may or may not be how they intended to come across. It is hard to read emotion in text. When possible, try to give the person the benefit of doubt or even send them a private message to see if it was a misunderstanding.