It seems to me the more mature a person is in the Christian faith, the more likely he is to do the latter and be led of the Spirit right into the "belly of the beast" of some of these mainstream spiritually dead congregations or atheist strongholds.
The Apostles, most especially Paul, were ever being led into the "belly of the beast."
Infiltration is the published tactic of the gay activist movement and I suspect now the atheist activist movement.
But considering the signs of times, I expect God to lead us away from them.
In this I think you are right....we are seeing the splits occurring in several branches of Christianity as a result of this infiltration... and rightfully so as the gays and atheists make inroads into the body of believers as well as other religious forms and practices which are often times pagan....new age comes to mind.
My brothers church recently left and now have a church of their own. Interesting is the Baptist church had helped them make this transition....and most interesting was in the dedication both denominations came together to celebrate. As the Pastor spoke thanking the Baptist Minister the Baptist Minister was quick to say ..."It is not us to thank but we you.. for showing us how it's done if the time comes where we might have to do the same."