In the real world, sure you can have horrible thoughts and be a good person. I'm sure there are people who write scripts for horror movies and volunteer at animal shelters on the weekend.
In the realms it would depend on whom you offer your thoughts to -- do you offer these thoughts as prayers to Bhaal or do you ask Tyr to give you strength to never act upon them. Unlike our world prayers are answered and thoughts are read so there are additional elements in the realms to contend with.
