The other day a friend and I were talking about people who make the sign of the cross as a joke as part of normal conversation. It has been on my mind since, and I've put some thought into why it might be bothersome.
If you've not seen it, it is hard to describe, but normally it comes about if they are "blessing" the activity of someone else or indicating someone has "blessed" something they are doing. Instead of saying "He said it was okay," they might say, "He said it was okay" and make a sign of the cross in front of them.
This confuses me. Oddly, it offends my friend, and she's not even Catholic. I'm not offended unless the person is obviously intending it to be a mockery of the Catholic faith, as opposed to something stupid someone does to be funny. I can usually tell. Regardless, I never find humor in it.
By the year 200, we have writings showing that Christians were using the sign of the cross. We use it now for blessings, as part of prayer, in baptism, and at other points for other reasons. Catholics use it a lot. It isn't just employed by Catholics, the same article notes Protestant denominations that use it. Some do it somewhat differently, and the Orthodox church goes "backwards" from what I'm used to. In any event, it is still used by a significant portion of the world's population to denote something holy, as opposed to something funny.
A fast Google search reveals not much in the way of official reason why not all Christians retain use of this physical form of prayer. Most note it was dropped after the Reformation because it was "Catholic," and I could see that. I think both sides of the aisle probably dropped things that were associated with the other, for good or ill. Some may also think it could be used by the superstitious, which is also true, but just like all things it can be thought of wrongly or correctly. In any event, many other Christians do not use it. One might theorize a grand scheme by which those who don't use it as prayer use it to mock those who do, and perhaps a few might, but that doesn't seem to be the norm.
I find its use in jokes to be odd on many levels. First of all, it is a tradition that dates back to at least 200. They were probably using it before then, but they didn't write it down. This is what the early church was doing, so even if we choose to stop doing it, I'm not sure mocking it is particularly useful.
Second, many use it during baptism or use it while saying what most people say during baptism, "In the name of the Father, the Son, and the Holy Spirit." That's kind of an important phrase. Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: (Mat 28:19). Whatever we think about baptism, most Christians don't mock it. Also, it involves the CROSS, which no Christian should mock.
I don't personally find it funny, though I am not offended usually. When I make the sign of the cross, I am reminded of my own baptism and also that I am set apart for the Lord. While I find peace and happiness in that, I don't think it appropriate for use in the mundane jokes one might make. At best, it seems akin to making fun of the way someone else prays. That's just not really funny.