The crate is not too small if he pooped in it.
Have they tried putting him in the crate for short periods of time and gradually make the periods longer?
Feed him in the crate. Keep his favorite toys in there. Make the crate the happiest thing ever. Never a punishment (which I'm sure they don't).
That's the only suggestions I can think of. We hand out a crate training pamphlet when we adopt out dogs. I might have one at home from when I got Taggart. I can check tonight and scan it in to you.