Tom,

As far as not letting paedobaptists into the membership of a credobaptist church, I have heard it argued this way:

If we let a paedobaptist into the church, then what will keep that person from becoming an elder? And the church would not want the paedobaptist to become an elder because the elders would then be in disagreement over one of the two ordinances given to the church.

True godliness is a sincere feeling which loves God as Father as much as it fears and reverences Him as Lord, embraces His righteousness, and dreads offending Him worse than death~ Calvin