Well, I suppose you could study the body language of someone who you know loves the US and then study Trump's body language and compare the results (this is silly). For me, I just intuitively know he loves this country. His narcissism, to me, means that he will want everyone to like him, which is why he's been telling Republicans lately that in 2018 he will be reaching out to Democrats across the aisle.
RE: In defense of Donald Trump