They're supposed to teach religion to their followers, not influence the outcome of initiatives and elections. The whole reason that the church laws were written into the 1st Amendment were because the Church of England comprised (comprises) 1/3 of Parliament and has a big hand in their elections and government processes. We didn't want that. When a church like the Catholic church and the LDS church want to sway an election, all they have to do is throw millions of that tax exempt money at it. It's not right. If they want to take part in elections, they can pay taxes like any corporation and be an individual like any corporation.
I think the argument that you make for/against Church involvement in politics is the same as unions or PAC's and many other Not for profits. In this case i Do Not think that it is good for the church to take this side of the argument. At best you have a couple of leaders that only represent a small portion of the church making the church less attractive to other members/potential members.
And by the way ST, churches are a different status of tax exempt organization (501C3) which prohibits much political involvement and donations, unlike PACS (501C) and unions (501C). They are specifically classified that way to keep them from throwing elections, such as the one for Prop 8 in CA. The LDS church is being investigated for violating its 501C3 status for their donations to pass that legislation.
