It can; you just have to draft rules to incorporate it into your game. The idea is mentioned in passing in the margin notes on YS250--Harry asks if you can gain mental armor via stunt, spell, or item to protect against the mental stress caused by casting evocations, and Billy says no, armor won't protect you against stress you deal to yourself. You could quite easily infer the conclusion that yes, you may generate mental armor via stunt, spell, or item to protect against mental stress caused by other people. Frequent contact with hostile WCVs would be a very, very good reason to want to develop such defenses.
If the holy symbol were an IoP or an enchanted item, I could see it granting you mental armor. If it isn't, you could still use it as part of a Discipline maneuver to grant yourself "My Faith Is My Shield," and then use the free tag to provide a +2 to your next defense roll, for instance.
Mental conflict is incredibly brutal. Re-read the description of mental conflicts on YS217-219. Mental consequences aren't "Embarrassed;" they are "Suicidal Thoughts."
Mental or Social Toughness isn't statted out in the books, but there's no reason to think they couldn't exist. I'd be inclined to handle a "Social Toughness" equivalent with a collection of stunts, since it seems plausible to me that Pure Mortals could have these types of defenses. You could handle "Mental Toughness" the same way, or just reskin the Toughness powers directly.