I'm not sure what you want Shaw to do, keep Seven locked in the brig once he knew Starfleet was infiltrated by changelings? Yes he's established as by the book but not to the point of ignoring all common sense when there are immediate threats that Seven would be useful in helping with.Once, and they were explained. Nothing is explained in this show. Nothing is spoken about. No consequences for any actions. Easy to pluck out moments of a show that lasted seven seasons and take pot shots at it.
There was a line where Shaw screamed out "Set all weapons to stun" or something like thatHe shot them in the last episode for feck's sake. Was shooting them all over the shop. The fella who was losing it in the holodeck with Picard and now he's dying for the same fecker who allowed Jack to escape the Titan in a shuttlecraft. Good lord.