If you don't buy one, you will need to be vigilant, see when gankers come in system, run and dock or be attacked. This costs you nothing.
If you DO buy one, you will need to be vigilant, see when gankers come in system, run and dock or be attacked. This costs you ISK.
Its true. If you don't run when they come they will say you were AFK. If you claim you weren't they will tell you to take it up with higher ups, who won't help you.
Don't be dumb and don't be a coward. Permits are MEANINGLESS except to take your money and laugh at you. And if you support gankers like that and non-gankers tell you to leave or they will destroy your ships, you deserved it.