It isn't fair to call them illiterate any more than it would be illiterate for me to not understand all the intricacies of real estate law. At some point, we as technologists gave them this communications tool without actually engaging with them in its proper use, and they learned the lowest common denominator etiquette.
When my teenage kids text me, I make sure that they use complete sentences. I'm a bit of a bastard that way, but hopefully they'll be better off later on in life.
It's one of the few potentially decent paying professions someone without a college degree can get into without insurmountable entry barriers, so perhaps you should go a bit easier on them.
College or not, anyone involved in deals involving hundreds of thousands and sometimes millions of dollars should not be writing emails that look like a text message written by a 12 year old. Perhaps I'm selecting the wrong measure of quality, but if a realtor were to send me an email punctuated by a plethora of smiley faces and three periods at the end of sentences, I would find another realtor. I say this based on experience, and the one that communicates with email that appears to be written by an adult turns out to be the one that doesn't annoy me by not listening and showing me houses I have no interest in.
It doesn't look to me like he's discriminating against realtors for not having gone to college; he's bashing them for actual demonstrated poor literacy, which is a lot harder to excuse than not going to college. (If you meant to instead make a more reasonable complaint about him painting with an overly-broad brush, you should have said so.)
