When people are rude or attack other members, please report the posts. Every post has a "Report Post" button on the upper right side of its top bar. It's an octagon with an exclamation point in the center. That sends a message to every GRF moderator and administrator, so that we know to look at the post and determine what action is needed. We can't be everywhere all the time - there just aren't enough of us - so we rely on members to tell us when there are problems. We can and will stop inappropriate behavior, but only with your help.
To stop receiving email messages about threads you have subscribed to, go to the User Control Panel (User CP button on the dark brown bar at the top of the main page) and look to the left pane, where you'll find a link to List Subscriptions. Click that and you'll go to a list of all the threads you receive messages about. For each title, click the box to the right side in the Notifications pane and then make your choice from the menu next to Selected Threads in the dark brown bar under the thread listing. You can change the frequency of notifications or stop them altogether.
I don't see a way to simply resign, but I'll ask and let you know. Meanwhile, you can post to the "Suggestions, Feature requests & Messages From/To Admin" forum to request having your account closed. I hope you'll decide against that, but this will certainly get a response.