I feel your pain! There's nothing more frustrating than spending all that time and money on perfecting your technique and gear, only to have it all ruined by an incompetent engineer.
I had to go through something similar on Saturday past, where the soundguy was the singer's dad. He obviously knew nothing about the PA, and of course the band felt as if we couldn't criticise him for fear of offending the singer! I couldn't hear a single thing on stage apart from the vocals, which were even drowning out the drums (shocking considering the drummer uses a LOUD acoustic kit) Of course, we still got our money and left after the gig, but I would hate to think that having bad sound out front would affect my potential income in future when people start saying "I dunno if the band were good because I couldn't hear them! I'm not sure if you should book them for your wedding mate!"
What annoys me too is that there are any amount of young budding sound engineers, just graduated with BSc Music Tech degrees and the like, who would JUMP at the chance to get experience doing what they love. Certainly, when I studied it at uni, almost everyone in my class had at least some knowledge of how to make a PA sound good in a live situation. Such a shame that people who call themselves professional sound engineers are getting gigs ahead of people who know what they're doing, based largely on the fact that they have contacts.