The Galileo comparison fails for two reasons:
1: Galileo's observations were not questioned, only his conclusions.
2: Galileo was also known for refusing to let many of his detractors look through his telescope, dismissing them as ignorant fools who would not understand the significance of what they saw anyway.
The proof argument fails for reasons already stated: the vacuum chamber test proves only that the suit works, not that it was ever used in space. There is no logical argument that if it works on Earth it was ever used anywhere else.
And the comment about only Americans matter is pretty much beyond belief. The US is a relatively young nation. I wonder how far he'd have to trace his family tree to find his almost certainly European origins...