If you draw a line at all (and some liberal denominations don’t), then you are just arguing about where the line should be drawn.
We draw the line at communing members of an evangelical church who profess the true faith. We do, however, admit to the table people who meet those standards who do not have a proper understanding of the sacraments.
I’m not offended that the Catholics fence me from their table, and they shouldn’t be offended that we fence them from ours.
With Lutherans, it is a closer call. They could probably take communion with us, but some, at least, would feel that I should not take communion with them. Again, I refrain, so as to not give offense, but I am not offended that they wish to limit communion to those that they know believe as they do.
I don’t understand why lines are drawn with regards to God and religions, in the first place.