The torture was necessary, because there's no way a solider is going to spill government secrets because they feel sympathetic. Revealing classified information is considered an unforgivable offense in any type of government position.
And if you really think about it: he's tied up; in a few hours, he and the other…

They were going directly into the library building to save part of their crew that got trapped inside without knowing how many walkers they were facing.

"But partying and screaming at cops because there might be a plague? Ridiculous. "