The Yiddish heading reads as follows: "The Yiddish Karate Kids."
I would see this as an interesting example of acculturation going on even actively within the Haredi community. The fact that the poster has Yiddish and features a Haredi looking kid leads one to conclude that the group is designed for and run by Haredim. Whether or not Jacob used martial arts to defeat the angel in Genesis, karate is not part of the Jewish cultural tradition. (We shall see what happens to Krav Maga.) Nor is karate a ubiquitous part of American culture like baseball or football that it would be impossible to ignore it. I would also point out that other forms of loose clothing can be used in karate besides for the distinctively non-Jewish gi garment. If you are going to take a stand against not engaging in gentile practices and wearing their clothing, this would be a logical place.
So we have Haredim reaching out and taking a product not only from a gentile culture, but one that is actually pagan (something that, unlike American culture, actually does raise legitimate halachic issues). Far be it from me to encourage Haredim to ban things, but there are too many obvious issues for someone not to notice. I wish this group best of luck. It would, though, be in their best interest to be honest as to what they are doing so not to give the banners a chance to create a moral high ground for themselves. If you openly support acculturation then no one can use it to discredit you. Up front intellectual honesty is always the best form of self defense.