... it may well be better to put up a fight now than try and defend your position later when you will be holding a much weaker hand to play.
If we put up a fight now, we have been told in no uncertain terms that BMI will not be integrated. That will give us a much weaker hand in the future when the separate company could be used to break a mainline strike (or vice versa).
That is why BA pilots want BMI pilots on the mainline seniority list.