Philadelphia fans have always had a reputation about being a "classless" fanbase. We still receive a lot of flack even though most our the incidents that involve fans are blown out of proportion. Philadelphians know that other fanbases can be just as "classless" in the stands, and apparently that is exactly what happened during yesterday's Eagles-Titans game.
At some point late in the 2nd quarter, there were apparently a group of Titans fans in the upper section of Nissan Stadium that were yelling for their team to try to injure Carson Wentz.
"Hit that leg" of course refers to the leg that Carson Wentz had a torn ACL in.
After going back and re-watching the end of the second quarter the chant wasn't noticeable on TV, so perhaps that means it was just a small group of fans who were trying to get the whole stadium to join in.
Because of it not being heard over the broadcast, national media likely won't be paying any attention to this. However, if Eagles fans down at the game would have said something along the lines of "hit Mariota's elbow" (Mariota is recovering from a nerve damage issue in his elbow), Philadelphians already know how quick word would get out to further deminish Eagles fans' reputations.