The extrapolations made were logical and or cinematic, as in the case of the visual of evil.
Evil is everywhere! Not just within the walls of that Jewish town so many years ago.
How it might be seen is imagined by Gibson. As part of a crowd, as a snake, as a tree.
As to making the Jews appear worse than the gospel, Gibson really softened that aspect. some biblical quotations were omitted and great care was taken to convey that not all were complicit, but only a few and even the High priests were not unified.