The transgressions of the past are in the past.
"Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come." - 2 Corinthians 5:17
We are all called to forgive trespasses, both real and imaginary. If we both concentrate on cooperating with God we will be cooperating with each other. First and foremost we each have to get past the idea that the other is an evil on par with Satan and attack that with is obviously and undeniably evil in our society.
Peace be with you.
Abraham Kuyper proposed a doctrine known as sphere sovereignty. I'm simplifying radically, but his view was that God operates through three basic spheres, that of the family, the church, and the state. The family is the most basic of the three and predates the others, and at some times in earlier history (Abraham and Moses, for example) the covenant heads in the spheres were identical.
However, under the current conditions, the government of the family, the church, and the state are and ought to be separate. That means while the confessions of the church quite properly prevent Roman Catholics and conservative Protestants from being in the same churches, that doesn't mean we can't work together to stop abortion, for instance, under the principles of Romans 13 in which the primary purpose of the state is to punish unbelievers.
If I were in an overwhelmingly Roman Catholic country (Cold War-era Poland, Franco's Spain, etc.) where patriotism and Roman Catholicism were closely linked, I would have significant problems cooperating with Roman Catholics. Roman Catholics in the Deep South had that problem a century ago as well dealing with the Bible Belt, when anti-Catholic efforts were made (wrongly) through Blaine Amendments to drive Catholicism out of the public schools which were at that point still largely Christian.
We're not in that situation today in America and we need to “hang together” whenever we can or we will most certainly be hung separately by the radical secularists.