Oh Boy.
The way skill points work in POTCO, the more hits you get in, the more rep you get. More rep points are earned if you are in crew. (for everyone in the crew)
What you are doing, a lot of Pirates consider Rep Stealing. You're tossing a grenade at "their" mob, taking "their" rep. You think you are trying to help by killing the mob faster, but in reality, a slow kill earns more rep, for everyone.
Please read this guide on
Grenades , pay special attention to the "DEALING WITH OTHER PLAYERS" section.
and this guide for
Reputation Chart and Guide
Lots of wisdom in those