Kane, I agree 100% with FPNY. After using the internet for over 12 years and dealing with so many online connection sites, I have learned a great deal, in that often what people write online or in emails or in text messages, sometimes can come out in a positive or negative manner, based on the “r
eader’s” interpretation of it.
Since I have placed and answered hundreds of online messages from various connection sites over the years, I have learned a thing or two about how to positively handle the situation you have described.
99% of the time, if I complimented a guy and he only said “Thank you.” and never commented about my photo or profile or never basically said anything else, I always wrote off those type of responses “from them” as they are not interested. So I moved on. Yet when I was in your shoes, I would say “Thank you.” and not add anything else to my message (when I was not into the guy who wrote me, if I was not into his photo or profile). Normally most guys take the hint of “Thank you.” or “Thanks” and they will move on . . . however about 1% of the time (in my own personal experiences), guys will write back and ask, if I want to meet them etc. etc. etc. after I just said “Thank you.” So what I would do is write back to them something short and sweet like “You seem like a great guy, however I do not think that we would be a good match.” Then “normally” 99% of the time, the guy will not reply back again or they may write back something like “Thank you for replying back and for being honest.” and then you never hear from them again . . . then there are those diehard guys that will write back
AGAIN and start spouting-off (in an angry tone) something like you don’t know me or who are you to judge me or what was it in my ad/profile that you feel that we would not make a good match? Then at that point, I never write those guys back, because if they can not take the hint and move on, I figure I’m dealing with a nut-case. I think that guy you were dealing with was definitely ad nut-case.
However I found that early on, if you are that blatantly honest with guys (i.e. saying I'm just not into "You"), often they will take offense and then seem to want to start an online war with you. Yet in my case, whenever I was online looking for someone, I was always nice to online guys (even if I didn’t like them for whatever reason). However the most I would ever write to a guy that I was not interested in, was just twice, and then I'd ignored whatever they wrote afterwards. Yet I always wrote nice & polite replies (if I had to write a guy for a second time, but that second time was my final time writing to them). Mainly, I always try to re-read my reply before sending it to a guy, to make sure I do not have anything in the reply to give him ammunition, in case he wanted to start a war.
Now with that being said, if you want to participate in someone’s war against you, then I say go for it and be brutally honest,
BUT be prepared for a lot of nasty insults tossed at you. Yet in my case, I had better things to do and I was not interested in getting caught up in someone’s drama about me rejecting them. When I have used connection sites, I never once ask someone why they were not into me. I always took a person’s hint and moved on. Since I am black myself, over the years, I have been thrown racial insults, simply because I was black. Yet I never let that bother me, since I’m used to meeting people that are racist no matter where I go . . . even on the internet.
Kane, good luck to you, but never ever let those type of online racist nut-cases get you down.

Best of all, it was nice that you found out this guy's "true" colors up front . . . can you imagine if you met this guy and liked him, yet to one day to discover this guy is racist?

Yet I will be honest in saying, that I have come across racist gay men (in my lifetime) who are only interested in black men for sex, yet they would never be friends with or be in a relationship with a black man. They only want sex from you, otherwise you are totally dead to them.
Wilson