"How does a secular celebration blaspheme anything?"
You seem to be saying that God is unoffended by the behavior of the godless, here. Either that, or you're saying that intentions matter more than end results.
One way or the other, you're mistaken.
You make no sense. The celebration is not anti-religios. It is not religion based. The 4th of July is not religion based. Thankgiving is really not religion based. Memorial day is not religious based. Labor Day is not religion based. New Years is not religion based.
And note that Kwanzaa is not and never will be a federal nor state holiday. So if you don't like it, join the vast majority of all people who don't celebrate it and concentrate your energies on things of importance.