Not to give them too much credit for just posting, but if even a single person on the fence about signing on saw his posts and got anxious that their SO would cheat on them while they're gone, then they've saved that person from making a terrible decision and, more importantly, saved the people who would've been personally harmed by their actions.

To defeat an enemy without firing a shot (except into their wife, heyoo) is the best form of victory. And it's effective. It's hard to combat enemy propaganda telling soldiers they're the good guys because the enemy generally has a stronger signal and a captive audience - but remind them of home while playing on their existing anxieties, and they'll be demoralized and less willing to continue the fight.

In case my perspective wasn't clear, I hate the US military and generally consider doing things to hurt or demoralize the troops to be not only morally permissable, but morally commendable.