Paul is talking about himself in Rom 4 and 14, because he was.
He writes in Rom 14:4; "I am convinced, being fully persuaded in the Lord Jesus, that nothing is unclean in itself. But if anyone regards something as unclean, then for that person it is unclean."
He wasn't pushing his personal stance on anyone, but in 1 Cor 11:31 he is talking about communion and how people were abusing that time for their own purposes AND they were NOT being circumspect when partaking. No difference correcting here than in 1 Cor 12 and 14....this is a big theme in 1 Cor.
Paul was instructing live and let live in context, he was not teaching to ignore God's Word nor the Holy Spirit.