Hi sweetbaby
I think being an activist against any Religion is a waste of time. We can offer people knowledge according to God's word but ultimately he will deal with all religions personally, all those that are false and the one that is true.
Acts 5:38-39 (New International Version)
38 Therefore, in the present case I advise you: Leave these men alone! Let them go! For if their purpose or activity is of human origin, it will fail. 39 But if it is from God, you will not be able to stop these men; you will only find yourselves fighting against God."
We can present ourselves as the one true faith as apposed to others that are teaching false gospels but ultimately the person themselves has to decide. But just apposing a religion because you personally hate it, feels unproductive to me.
If I left a religion because I questioned it's teachings I wouldn't become an activist. I would spend my time more productively searching for God's true faith.
And I have to say Simon makes a fair point as well.