Goh Meng Seng will not find many sympathizers if he cannot find something relevant to argue against WP that are not applicable to others. Everything NSP under him achieved, WP achieved and more. I cannot think of anything any party has achieved that WP has not. So if he criticize WP much more than NSP or not at all NSP, people will conclude that he is sore and therefore biased.
Don't get me wrong. I am pro-worker but not necessarily pro-WP. That is why I use a hammer different from WP's hammer. From time to time, I will criticize WP when the timing calls for it but overall, I like this party.