One of the problems is Di Blasio singling them out and not the other crowds that get together on twitter.
The other problem is that these religious Jews, whom I love, are committing a huge Chillul Hashem by not following instructions during this crisis which does lead to death, (including the beloved rabbis of whom they are mourning for).
All it does is add fuel to the fire of Jew haters and that's the last thing I want to see happen to Jews like these.