I have to say that although I am an atheist who is very critical of religious institutions and although, bus or car allowing, it would be nice to have a replica of the Ritzy in Crystal Palace, I don't feel comfortable in supporting this petition to try and thwart the plans of this particular religious group.
I just think its a bit mean to be honest. Whether a change of use would be granted or not will largely be dictated by planning policy and a petition won't help much as I see it.
If a church or a cinema there will probably still be the same planning issues resulting from attracting people to the building and a religious establishment is more likely to be the less offensive and disruptive option in strict planning terms. However if this is already designated an employment site then it could be argued that a cinema would provide more than the church. Was this building ever a cinema, as many bingo houses tend to be?

I think this action could be read as simply a tug of war between what is very probably a black-led religious group and the overall white Ritzy loving middle classes, (myself included in the latter category).