If he didn't run towards the pill box I probably would've engaged him but whatever, I think the reason for the rule not being more clear is they don't want the rule list to be longer then it already is.
"Misuse of suicide vests to kill restrained players or destroy vehicles for no reason may still result in administrative action."
I get it's a little grey but that's where experience (and mind reading) comes in of knowing the grey areas regarding the rules, there's a slew of things in there that are rule breaks but aren't explicitly written