There are many ways for people to get different kinds of christmas cards so, if certain people want to produce political christmas cards, and other people want to buy those same political christmas cards, there isn't really a reason why they should not be made, or should be banned all together.
I think that it's fine for a card maker to produce cards with a political undertone in them, if the market is there and people buy enough of them to make them profitable then it's just an example of the free market at work, I think people are smart enough to recognize the political messages in cards.
Some people like that sort of thing. It would behoove the person sending the card to know what the receiver likes. You do not want to send a card making a political joke that is going to upset the person receiving it. It is probably better to send a standard Christmas card.
Christmas should be a religious holiday without political undertones whatsoever. Sometimes, we need a break from politics so we can just enjoy life and enjoy the winter holidays. Christmas cards are for spreading holiday cheer and not for promulgating a particular political ideology. If I ever get a Christmas card with a political statement, it goes in the trash.
I do not believe that Christmas cards should have political undertones to them. I think that it is important for some people to just let Christmas be about people enjoying the holidays. I think there is already too much politics. There doesn't need to by any in terms of Christmas cards.