The entire premise of Trump’s campaign is that America is not currently great. He talks frequently about how often we lose. He and his supporters are very clearly angry and dissatisfied with the current state and path of our country. Heck, he’s recently spent considerable time telling African-Americans that their lives are miserable (poor, unemployed, shot if walking down the street)
Why can he criticize our country? He’s (allegedly) wealthier than Kaepernick. It’s unclear what sacrifices he’s made to improve the situation (as is being required of Kaepernick). Why can Trump point out that it’s not great being African-American, but when Kaepernick does so, he should find another country (Trump said that)? If you’re going to completely ignore Kaepernick’s point because you disagree with how he made the point; you’re part of the problem.