i have had the same problem you described. people have on occasion mistaken my caring for romantic interest. of course this is not our intention; we simply care for people, sometimes intensely, and we feel (or see) a need to express it. in highschool, i hated the game most people played... the game that caused everyone to automatically, constantly, subconsciously be on the lookout for romance. what in the world? how can you live that way, with all the turmoil and silly drama and actual relational danger it causes???
back on track: you and i have the same combination of two particular traits: the ability to care genuinely & deeply for people without any romance involved at all (often for people of the opposite gender? correct me if i'm wrong), and also the ability to express it confidently (i mean, we are confident that what we are saying is true, because we've thought about it carefully). the problem is, most of the world doesn't recognize that for what it actually is. the brutal truth is, people simply aren't accustomed to people 1) genuinely caring for non-selfish, non-romantic reasons, or to people 2) saying exactly what they mean. we happen to do both of those, sometimes simultaneously.
it's easy to see how that could cause problems.
therefore, in order to mitigate against both the occurrence of as well as the severity of those problems, i suggest we come up with a new phrase, one that will very clearly define (i.e. limit) our motives and our intentions, while still expressing the fullness of our emotions. feel free to give a thumbs-up to one or more of these, or to come up with some yourself. at some point, though, we need to settle on one and use it.
okay, ready for these? of course you aren't. here we go anyway:
"i care for you as much as a human could care for an intelligent, sentient, but non-human being. (it might as well be physiologically impossible for me to be romantically interested in you, but still, i would totally give my life to save your planet from annihilation if the opportunity arose.)"
"you are important, even priceless, to me... as is our friendship. i would never want to hurt you. if you ever make a pass at me, i'll punch you in the gonads." (please note that that one works for both genders. 'in the face' didn't seem intense enough, and really, the gonads are the most apropos place to punch someone who makes an unwelcome pass at you.)
"i long to spend time with you, get to know you better, form a closer friendship with you... as long as it gets no 'closer' than, say, two feet or so. (i will occasionally allow a side-hug.)"
"i love you like earth's asexual plant-life loves itself." (this is not to be confused with hermaphroditic life-forms, which contain both male and female gametes. asexual creatures are genderless and therefore do not desire either romance or sex.)
i know what you're thinking: 'isaiah, ALL of these are so good, i simply can't choose between them!' well fear not, brave reader, for i have saved the best for last:
"i love you-- not like a fat kid loves cake, but more like the chef (who makes the cake) loves the fat kid."