False. Difference between 1h infantry and 1h cavalry (with lance or not) 18/18 build on lvl 30 is 5 if traded for 5 ridding, perhaps even 1 shield or wm or athletics (depends on the player style of combat). Lacking those skills don't handicap cavalry on foot much, pure infantry can withstand an additional hit if it's lucky, difference between 5 and 6 shield skill is so hard to spot in melee it's not worth mentioning.
Actual danger to the character using light cavalry is smaller than innate danger of infantryman. Every player that act as retard is in danger, cavalry is not exception (and even then cavalry can disengage quickly).
18/18 build for cav? Perhaps as a balanced anti-infantry build but as an anti-cav build this is underpowered. My current anti-cav character has 9 riding and a heavy lance, getting most of its damage from the speed bonus rather than PS. You also don't seem to consider the cost of gear that people are using. Assuming a budget of 45k much of that is already used by a horse. This affords less cash for top tier items and so puts riders at a general disadvantage when dismounted.
As for the whole "innate danger" idea I'm going to redirect you to the other cavalry thread where I posted about this. Anyway, these discussions are getting really tiresome. I think I'm done with these forums - at least for a little while. Bai'