I personally think they should not because it can do anything to stop PAP from reversing their decision but to let PAP pay the maximum political cost. I think even the middleground are unhappy with the fare hike and it silly for WP to withhold their fire just to make themselves appear moderate in the eyes of the centrist voters.
No doubt there will b no reversal, but it forces debate n justification. So far, PAP just highlight the sweetener which is rebate for under privilege which obviously bring them brownie points.
But if WP isn't gonna ask Lui to justify the increase n on wat basis, public won't know. Already WP is behaving sensibly by not challenging for sake of challenging but on issues like this, they should make it a point to seek justification or at least let Lui sweat
The other subject to bomb PAP is the privatisation of hawker centres.
It's clear at the moment WP lack the clout to successfully block any measures passed by PAP but it can be a thorn to always keep them in check, to remind voters that they r on the back of PAP else come 2016 pp, will forget,cause PAP will give ang pows