I don;t understand the reluctance to have a quiet word with him about the situation. If it's as cut and dried as it seems, the worst thing you can do is let him keep doing what he's doing. No need to write him off in front of the lineup, but if he's a danger mouse it doesn't matter what he's riding - he needs to be told.
There are far too many middle aged learners on all manner of craft who don;t understand the ocean sufficiently to be anywhere near others, or understand etiquette/lore. It's pretty straightforward, unless they're covered in tough stickers and missing teeth of course....