I was raised the same way. I had a brother-in-law die who was a real SOB to his wife (my husband's sister) and I felt no desire whatsoever to speak well of him after he died. I held my tongue but knew if I ever did talk about him it would not be out of a phony sense of respect I never felt for him in life. So here it is 10 years later and I still haven't talked about him which is my respect for those he left behind, not him.
Oooooh, and it's HARD to hold your tongue when someone else is just going on and ON about the "dearly departed" and you're just hoping you can hold off smacking somebody! I know what you mean!
Especially at the funeral. But I guess it's worth it not to get beat down by my mother in front of the entire family.