According to his stats he wasn't inactive, also it's a lose-lose situation anyways if you just admit you yeep inactives in your alliance..
And even if he had been inactive, you don't just let go of cities just like that, heard about tripwires?
Active is an odd term in Grepo, logging in once or twice a day is not really active unless online for hours at a time.
Maybe he just set militia before logging off for the day...
I tend to set militia every time I walk log off in these early stages.