I feel I should be polite when I turn it down.
As to accepting stuff, do you mean polite as in saying "Thank you"?
I think the post was asking if when you receive free stuff should you post nice things about the game.
This is an issue I do have with people receiving free stuff, how do we know their opinions aren't based on getting free stuff? Not saying any are mind you, but if we the watchers know a youtuber making positive sounds about a game gets free stuff from the game maker does this influence the way we, the watcher, interpret the content being watched? As I said earlier I do watch your videos but not Yamik's, this is purely a personal decision based on style and method of delivery rather than what is actually in the content. If you both post about the same thing I will watch your content rather than Yamik's.
There's a lot of complaints at the moment about "free" stuff on the forums, people getting free "Horizons" when other had to pay for it and it gets quite nasty in some cases, I am against "free" stuff that other people need to pay for simply because of this toxicity that it inevitably creates and would prefer that content creators got stuff that other people didn't have access to at all, like early access, tours of the offices, still and images from upcoming content and etc.
But in the end "free" stuff is entirely up to FDEV to dole out and how they make that decision isn't necessarily our business to know.