True things aren't the best. But what did you exspect? Also, Sarah is not worth more than humanity. Just to make that clear. Had the soldier let them in they may have been infected and destroyed the QZ and ruined humanity's last hope. Had he turned his back on them you bet that Joel would kill him and sneak in with his daughter. What if his daughter or even him were infected at that point? He'd doom all of those survivors. To take such a risk is not cool with me. Endangering humanity's survival because you want to live.
And about that martial law thing and it not working, it's because people like Joel aren't stepping in line that its flawed. The soldiers got their hands full trying to keep the QZ together with all the outlaw gangs and fireflies running about. My point is if they'd just settle down they'd have no such problems, instead it'd turn into a situation where he could be part of the military trying to ensure the survival of the people living in the QZ. The military isn't doing anything wrong, they're trying to contain the situation at their best. Also, you thing supplies are just lying around to be found? Its been 20 years ofc the supplies will be running low but instead of dooming other people to get out of hte situation you should work together with the military.
The military is only "evil" because you made them "evil" in your mind.