More concerning than your buddy ingesting a little yeast is all that aroma/flavor lost when not using a glass.
He's not getting a full sense of the beer you spent all that time making!
Yeah dchokie's right, there's nothing wrong with drinking the yeast.
The yeast in the beer is not a bad thing, in fact it is full of vitamin B complex. You can buy it in many healthfood stores, and the Belgian's practically worship it for it's healthful benefits.
But most folks, especially Americans who for generations have been weened on crystal clear, pasturized and filtered "dead" beers like BMC are frightened of the cloudyness and yeasty taste of bottle conditioned beers with a lot of yeast in it.We have been encultured to be used to bland, tasteless, massed produced pablum, so many folks are downright scared of "Real" things that may be sour, or raw, or earthy.
But if you're not used to it, if you've never drank a lot of bottle conditioned commercial beers (which have sediment as well) folks do have issues, initially, dealing with the oligosaccyhrydes in yeast, so folks in the beginning do get gassy, or some, have GI issues, but eventually we tolerate it.
Just look at the threads about yeast farts and you'll see. We've all gone through it, and our gut's gotten used to it. Some folks may have the S**ts initially from them, but that's in rare cases.