Desert Raiders won't do too much damage in range form to the knights, but when it comes to melee, that huge base melee armor alongside the damage and the debuff is going to be instrumental to them.

If you're feeling pressured as Ayyubids going into castle age, going for the military reinforcement wing and getting three dervishes with the veteran upgrade can absolutely butcher French knights.

Camel lancers are actually worse against knights than desert raiders.

Camel Lancers minus 20% damage for all horse cavalry. It's pretty significant when that's the entire thing your civilization is based around, like the French.

If those camels do get hurt, they just run back and get healed back to full. French knights need a pretty expensive upgrade to heal themselves; Chivalry is not an easy investment for the French.