Sensitive subject. Could it have a positive meaning?

Hello. 
I faced this expression and i don't know, can i use it in a positive sense or not. I took a dictionary and found out that it has a negative meaning. Something that we don't want to talk about, because it's painful.
So, maybe the negative meaning is more common, i don't know.
But could i use it in a positive way?

For exmaple.
- Do you like cars?
- Oh, this is my sensitive subject!

*It doesn't mean that a guy was hit by a car in the past and spent a few years in a coma. He just loves cars and can talk about it for hours*

If i can't use it in a such way.
So what is it called in English? A topic i can talk about without a stop?

Thanks for answers.