Do you have any data or reason to believe "unionized European programmers don't get paid nearly the same as un-unionized American ones?"
Does it show which of these are "UNIONIZED European programmers" and how many are "NON-UNION Americans?" If not, we can dismiss the claim outright.
All you can say at that point is "I'm too lazy to confirm or disprove it". If you want to disprove his statement for real, you're going to have to put in some effort looking things up.