"I never quite got the Kaepernick hype or the Kaepernick hate. He was a two-year wonder whose game was figured out quickly by the rest of the NFL. However it was always amazing to me that certain people found it perfectly acceptable to rip him because of his politics. The way he express his political ideas certainly isn't the way I do, but the people that rip him for that have to realize they are being bullies, right? Hating someone for his political beliefs just because you disagree with them is wrong on so many levels. Unless you understanding of your own politics leads you to do awful things against others, who cares. Lots and lots of NFL players are political. None of my business."
The answer, in both cases, is the same: Once you publicly take a stand on an issue that can cause controversy (religion and politics), some people will criticize you. In this day and age, the criticism will be extra loud because of how polarized every debate is and because EVERYONE has an outlet to express that criticism.
Tim Tebow is not just religious, he is annoyingly religious and his faith is part of his marketing gimmick. Kaepernick built a brand around his activism. One has been black balled (and isn't worth the trouble to carry as a back-up), the other is being giving free opportunity after free opportunity in different sports just because. Some people will see a double standard and say the situation reeks of priviledge. The group that likes Kaepernick will hate Tebow and the group that likes Tebow will most likely hate Kaepernick too.
Reality is, both are ****ty players that have became symbols for one of the two "groups" in the United States. That makes you a lightning rod... and... at the end of the day has very little to do with religion or race equality.
Personally, I have nothing against Tebow being over-the-top religious or Kaepernick taking a political stand. Mostly because, well, I am not American. I can take a distance from the whole thing and just look at things for what they are. There are huge cultural issues in the US and they go far beyond those dudes who, for whatever reason, became symbols. It is sad, really.