The generalisation isn't the problem. It's entirely possible that 90% of the people he dealt with were complete beginners. The problem is referring to those people as "tech-handicap". That isn't 'brutally honest'; it's being mean.

A good product evangelist is someone who can talk about the people they've met in the same way regardless of whether or not those people are still in the room. That is the skill that makes you good at evangelising something - if people like you they'll listen to you. If people see you being nasty they won't, because they'll wonder if you're going to be nasty about them once they leave.