I think it can sometimes be wrong. My mother was a firm believer, but I'm not sure that she was actually in the 'unshakeable' category. So I always tried to be careful, when discussing religion and theology, that I did not strive too assiduously to instil doubt in her. I think that would have been cruel, since her quiet faith meant a lot to her.

That said, I think in most cases it's not wrong to try to cause doubt, and it certainly doesn't make it right to force people to believe stuff.

No its not wrong to get believers to doubt there faith. We are trying to lead them to the path of enlightenment. To free them from brain washing.