"That is one of the many qualities that make him the man we love to celebrate."
It's a simple case of subject verb agreement. You know, "the dogs eats" verses "the dog eats." If you take out all the extra words, you will discover that the subject of the sentence is "one" and the verb is "make." Obviously "one make" sounds funny. It should be "one makes." Right?
Wrong. If you followed that logic and believed it, then you are equal to me in grammar prowess because that is what I thought to be the case and it is incorrect; we got nothin'. In fact, the reason it has taken me so long to post an answer is because it really doesn't make sense. I mean, the subject is really about the qualities, but that appears to be in a prepositional phrase, which often tricks people into thinking it is the subject when it is merely describing the subject. The average Joe would read that sentence and not even consider it to be grammatically problematic...and Joe would be correct. That's what I get for over-analyzing everything; problems created out of nothing.
Yes, I am telling you that I lied. There is nothing wrong with the sentence. I quote to you from the book ACT 36: Aiming for the Perfect Score. (Yes, I read such books in my spare time...don't ask).
"Words indicating amount, like the word none [or in our case, one], when used as the subject of a sentence, do not hang out in the Singles Club. They are married to one word--the word of. The noun at the end of an "of" phrase [qualities] dictates the verb status [make]."
So there you have it. The sentence is actually grammatically sound. Psych.