there's enough of them that, if they crossed to the ndp (or the greens), they could undo the liberals' majority. this would have substantive consequences in terms of limiting what carney can do regarding issues like his attack on labour rights. it would force him to rely on conservative support, which is bad optics.
i would encourage liberal mps that oppose carney's attack on labour rights to leave the party and put an end to this very false majority government. carney is taking advantage of the situation to seize power and ram through legislation he has no mandate to try to ram through. backbench liberal mps that have been rejected by the government for being too left-wing have the power to stop him by joining one of the other parties instead.
as for the bill, i would probably have supported the idea, but likely have had issues with how it was worded. i would be more interested in preventing arms exports to more active conflicts in sudan and especially, particularly blocking canadian arms exports to ukraine, which we know are being used to enforce conscription laws at gunpoint, than i would be concerned about canadian arms exports to israel (which are minimal to nonexistent) and would have argued for broad language in the bill for that reason.