I don't think it should be criminal to wear a t-shirt actually. In normal societies these kinds of people would be shunned. However, France is screwed and overrun so it is therefore not normal.
The court ruling didn't mirror the sentiment of the community.
As the mayor says:
"I have
the feeling that the law does not reflect reality as it is seen by
citizens," he said, adding that the ruling "gives the impression that
everything is allowed."