Freaking snobbery. And wrong. Just plain wrong. Landscape mode is very useful in portraiture, it just takes a bit more attention to things to make sure it works well.
There's nothing wrong with landscape portraits and I like what he's trying to do. A whole bunch of options exist to make that picture work better within the Landscape mode, or maybe he can try square, with the subject on one side and something to try and build the magic triangle. Maybe he can try an aperture with a shallower DoF to bring more focus on the subject but still have some surrounding stuff. Maybe he can try fill flash. A lot of options for suggestions other than "you've obviously never taken an art class" which makes you sound like a boob.
Perhaps rather than name calling you could provide your own example of a portrait taken by you in landscape orientation to demonstrate what you mean. That may show Elizabeth the way. Very few of the landscape orientated shots posted have worked as there is too much dead OOF space. As I have said, landscape orientation
CAN work, but it must have a compositional reason or else it doesn't work very well. Cutting off body parts to get a landscape orientation never works. Keith isn't showing snobbery, just applying the principles. Your self righteous attitude helps no-one.