As a trader who has recently been forced to drop my cargo by XA I say that the demanding cargo is perfectly in line with Xeno motives; Disrupting/discouraging foreign trade so that the jobs come back to Liberty.
I do agree that in cases of human cargo that you might find an alternate way of hurting the trader without mass murder of passengers, etc.
Id also like to see the occasional incoming foreign trader attacked and heavily damaged before being allowed to surrender his cargo. Just to help get the point across that foreign trade is bad for your health and your wallet. (should I remind them that Im a Liberty born trader?) :)
Whatever happens I personally think the XA have been doing a fine job RPing their faction.