Jesus wasn't concerned to prove anything. When people asked for proofs concerning him or his truth or his kingdom, he refused. Instead he called disciples into his company, knowing that life in his company would generate conviction and assurance of him, his truth and his kingdom. Another case in point. The ideological left sits loose to morality.
Morality is thinly disguised social convention.
As social convention it reflects social class rather than some truth or other etched in stone. The ideological right, on the other hand, equates immorality and sin. The immoral are the real sinners who especially need saving, while the moral, of course, are virtuous and godly. Sinnership is common to all of humankind, whether moral or immoral. Our sinnership is the same spiritual distortion whether we behave in a manner which others congratulate or in a manner which others curse.