I don't think you suggested that either and no, I don't see anything wrong with asking someone if they have repented and submitted to Christ. But I don't think communion should be withheld from people when we simply don't know what's in their hearts.It is impossible to judge a person's "relationship with God". I don't think I suggested doing that. But if they are strangers we can ask them about it --- ask them whether they have repented and submitted to Christ. Anything wrong with that?
I agree with the 1 Cor 11 verse Homer quoted above: "Let each man examine himself".
I agree with almost everything else you wrote about judging the sinful conduct of those in the church up to and including ex-communication. I do believe the scriptures support it and that Jesus taught it (Matt 18 ).