I'm going to have to agree with everyone else on this one and say no as well. The fear spell is magicaly based, therefor class is irrelevant. However, if you were to say maybe dwarves should be innately immune to the effects of the fear spell, that might be slightly different. Still though, I'm going to have to say Minette worded things quite well.
If we're going to talk about additions to the paladin class, I thought of one thing that could be slightly handy. I'm not going to claim this idea as completely my own, but I can still easily imagine a paladin of Ain doing something along these lines:
'Shield Slam'
Syntax: Slam <target>
Shield Slam is a skill where a paladin utilizes his or her shield that he or she currently has equiped. A successful shield slam will briefly stun the target for a short period of time, as well as distributing a moderate amount of damage depending the level of said shield. Continuous use of shield slam however, might result in wear and tear on your shield, depending on the material it is made of.
Edit 1: I imagine that the shield slam skill would have about the same success rate as trip would, but with a tiny bit more lag, wether it was successful or not. Of course it would require the use of physical energy. However, if the attempt were to fail, it would result in the momentary loss of balance, disallowing the paladin from using any other skills for a brief amount of time.
This is something that kind of just came to me while I was out having a cigarette break one day. I apologize if the post is not entirely perfect, as I am doing this on my phone at work