You can't change the way someone else feels, you have no control over whether this guy has feelings for you or not. But you can establish boundaries over whether or not you accept his displays of affection/his feelings towards you. Have you said to him that you only want to be friends? That you are not interested in any relationship? Being clear with the kind of relationship you are able to give (friendship only) is the first step. Calling him your friend, sending gifs/images that insinuate (or directly mention) that he's your *friend*. Unfortunately, for women things don't always stop here because men think that eventually they can change women's minds (which, sure, sometimes they can, but sometimes they can't) - frankly, to me, it's just disrespectful if a guy ignores your boundaries and pursues what he wants despite you expressly stating you're not interested. But, so much popular culture and society enforces this shitty behavior in men.
Anyway, I digress. You also have no control really over whether a guy gets his feelings hurt from you rejecting him or not. Of course, there are ways to go about letting him down that are better and more considerate than others, but also at the end of the day, he is responsible for his reaction and behavior, not you. I have had guy friends express feelings for me, and coworkers too, and usually initially I just subtly avoid or dance around any sort of advances, hoping that they'll get the hint and stop pursuing. Talking about being interested in other men helps - or in your case, talking about not being interested in anyone at all whatsoever, no exceptions. The indirect but obvious statement that in your mind there is absolutely zero thought of him in any sort of romantic, sexual, suggestive way, should also start to clue him in, without directly rejecting *him*. But, if all else fails, and he's still giving you compliments and suggesting that he's into you as more than just a friend, and it makes you uncomfortable - AND you really cherish him as a friend and want to maintain the friendship - then just be real, up front, direct with him and say that you're just not interested in him in that way, but you do care a lot about him as a friend, and that you would like to keep the friendship going if he's okay with being just friends too.
