That clause is only valid for LRP, on MRP there is no half completed objectives clause that allows you to murderbone, only your initial objectives can grant you that status.
I mean, they weren’t really on to you as much before as they were after
Doing what you did when cornered by sec is okay, but going out of your way to attack sec with plasmaflooding is not so okay, especially considering that your objectives were nowhere near related.
Your ban is lifted now, have fun being an antag again
Security is always valid to antagonists that are allowed to kill (basically everyone but abductors) but it must be done in a low-collateral way such as one-on-one fights, drugging and dragging into maints, and small explosive or bear traps. Plasma fires and large bombs are not low-collateral
Being attacked doesn’t change the above, but if you’re cornered and out of options, desperate actions become more appropriate. This means dragging a plasma canister or bomb around with the intent of using it when being attacked is bad, but running to toxins storage while being chased in a hopeless situation and opening a canister after sec comes in is fine.
Thanks for clarifying the issue in a more general sense, my replies above were limited in scope to this particular appeal and situation and could easily be misinterpreted for other scenarios.