I think your desire to respond and to ease feelings of rejection in the person whom complimented you by contacting you is admirable and sweet. However, making up reasons to say "no" isnt. Most of us recognize a turn down when we see it, and giving reasons that are not real is a little insulting. I prefer a simple "Thanks for the interest, but I dont feel we are a match". It is honest, polite and cuts to the chase. I have had rejections that were honest and helpful like "take it out of your profile tha you have 14 kids. Thats a real turnoff."
I had not even considered how intimidating that could be to a man, because they are adults for the most part and off living their own lives. But I realized then that could be the reason for other rejections. Did I take it out of the profile? No.
But it did give me some insight. Another man said "redo your profile and change your age. You can get away with it and most men dont want someone as old as you Again, while that should have been obvious to me, I was not focusing on the fact that many men my age want much younger women. I blithely thought that since I preferred people with the same cultural frames of reference, that men would also. His comment gave me valuable insight into how many men think, and it was helpful. No one has ever said, "sorry you are just too fat, old and ugly for me", but when someone says "oh the distance is too great" or "I want someone who golfs" I assume that he really means "too fat old and ugly". My point is, if there is a real reason, such as your family is just too large", that is useful. If its just an obvious phony brushoff, its insulting.
But any reason is better than the impolite no response, which I must admit I am guilty of as well, although I try to give some response most of the time.