Judge a player on how good he is? -yeah that's the first consideration obviously Derek but then because we are all different we add our own ideas and experiences into the mix, sometimes ill-judged, sometimes not. I gave up years ago applying a filter to what I say. I just put it down and as you once told me, don't worry how people respond!
A few years back I was in charge of a factory department , with Poles and Cornishmen working on two separate areas of machines. The Poles were producing 3 times the output of the others, so I decided to mix them together with great results. The attitudes of the younger Polish guys influenced the team as a whole. However, one of them actually explained to me that, as you stated, only those with good work ethics come over here not lazy types.
I think you can, to some degree at least, judge attitudes on origins. In my time in the Navy I remember Scots and Geordies being far more up for it generally and usually ahead in the promotion stakes.