How to get rid of a bad thought?

The worst thing you can do is keep dwelling on the bad thought. And just as bad is concentrating on how to get rid of the thought. The best thing you can do is engage in some favorite activity that takes some concentration to enjoy. It will take practice; the bad thought may not go instantly. But as you get used to the process of concentrating on something fun and/or useful, you will discover that the intrusive thoughts will come less often and will not be as difficult to control.

You also may have to deal with the reality that you may really enjoy the bad thoughts. That is human; don't beat yourself up. You know that you can enjoy any thoughts any time you want. If you don't want it at this time, then do the above.