Nah, Marx is dumb.
It's because single people, or at least those who are single but don't want to be, don't have a choice except to observe Valentine's day. If you're in a relationship, you can make the choice on whether or not you and your significant other want to celebrate it, or if you just want to do what you always do. If you are single, you have to confront all the potential lives you could have led with all the people you could have been celebrating Valentine's day with, or you have to act stubborn and defiant and declare that you don't care about the stupid holiday and pig out on chocolate, which is really the same thing.
I mean, ultimately what I just said in that last paragraph is completely wrong, and you don't have to do anything or feel anything that you don't want to. Humans have free will and all. But you live in a society that tells you that you need to be in a relationship to be happy, and, whether or not you agree with that, if you also happen to want to be in a relationship, then Valentine's day is just a reminder letter from society that you aren't the living up to the life that you want to live.