his SP ignores & then the character can't use stealth. does it do this against the Batman Ally TA as well?

Yes. The Batman Ally TA allows the character to use Stealth. First, Light the Danger allows Green Lantern to ignore the Stealth. Then Light the Danger prevents a character that takes damage from Green Lantern's attack from using Stealth that turn.

From the Player's Guide:

ok, great. thanks! i figured it did but just wanted to be sure.