How to build a bridge -
Establish a need for the bridge.
If there is one -
Find the gap that would offer the greatest benefits from a bridge.
Identify the points best suited to support a span.
Build a bridge and span that gap.
Many along the spectrum of religions, no religions, no opinion either way could stand to benefit from the construction. Sometimes in unexpected ways, I suspect.
One off the top of my head is our support for the separation of church & state. To stretch the analogy, lol, that issue has become increasingly compromised by a small, but swift flowing current. That one needs to be bridged by all who support that standard.
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When you build that bridge you start building on the left side of the river and the right side of the river at the same time. You find the best place to build that works with both sides. The goal is to meet at the middle so everybody can benefit from the bridge.
So if the far-right is miles from where the far-left wants to start the bridge we need to look for a new place. 
Sometimes it's easy and sometimes it's hard and sometimes it's downright impossible.
When it becomes clear that it is impossible, I think it may be time to call it quits for that particular location. Things may change and you may try again later, but there is something rather crazy about continuing to engage in a project which has zero hope of being accomplished.
