The straight hair - big deal. Many Jews have straight hair. Some even have blue eyes. But frankly, I don't remember Jim's eyes being blue in the film. I remember them being brown. Am I wrong?
You're not wrong. Gibson had Caviezel wear brown contact lenses in the movie because he anticipated the objection that "First Century Jews weren't blue-eyed!"
Of course, he anticipated the objection also that the "Passion of the Christ" was "anti-Semitic," and tried in good faith give no grounds for that objection in the movie, either.
Gibson could have cast Denzel Washington as Jesus, and this letter writer would have complained that he was "too light skinned." He could have had all the Jews in the film with nose jobs and perfect teeth, and he would have been accused of portraying Jews as "rich elitists." People like the one who wrote this letter have an agenda which they are not going to let facts or attempted accommodation obviate.