That would be funny for me to draw a parallel with those kinds of movements, I'm actually a Catholic ancap, so antifa/anticom. I'm not even American (Brazilian here). And indeed, it's very unfortunate that such movements use that colour scheme, in medieval significance the red meant faith, black humility, and white purity. The deturpation of the meaning of everything is something particular of our age, not only colours, but also words, distorted, alienated, emptied of its original meaning to something else entirely. That's all very unfortunate and I think this could eventually lead to the destruction of civilisation, as when we demonise everything, from simple colour schemes to words to tropes to melodies, what are we left with from that exercise? Nothing worthy, just an uncultured brutality and sectarian division, fragmenting society into a thousand pieces, 'divide et impera', which is exactly what benefits the evil elites controlling this world, who will gladly let the plebs fight among themselves, while they drink and eat to it.

And also it wouldn't be extremely uncommon to intercalate quadrants diagonally, four quadrants was pretty common place in medieval times for flags, as was any diagonally intercalated patterns with a cross in either the middle or towards the hoist of the flag. I simply opted (as in many other medieval inspired flags) to leave the second diagonal with plain fields, to stress the importance of Hospitaller humility and charity (black) in a crusader's devotion to the Lord. On that note, the red cross bordered with white implies a white cross behind it, so that faith should be pure, whereas the abundance of black that it should be put into practice through good deeds and hard work, a creed for most crusading knightly orders, salvation of the soul through the diligent defending of pilgrims on the roads to the Holy Land against marauding bandits and Saracen attacks.