After the Israel lobby destroyed the party at the last election, they know who their masters are. If they go pro-palestinian, the attacks and media pressure would be relentless.
What’s worse is that it would subject the UK to more Tory misery, its unfair but its reality, Tel Aviv will tell Britain how high to jump and Britain will jump exactly that much.
We live in a world where lifelong anti racists are cancelled for racism and watermelon t-shirts trigger existential crisis, not calling for a ceasefire is just reducing the political attack surface as any lobby would have to attack both parties holding the same policy.
If the icj somehow rules a genocide some many years later, they will all have been complicit but there will be little consequence.