I do agree with your sentiments about all workers at the end. I suspect your heart is in the right place, so please don't take the following as an attack but rather friendly advice...
Justifying the low wages of one worker by pointing out the even worse conditions of another isn't an argument that arrives at the conclusion that all workers should be properly paid. Effectively, it comes across as if you're saying 'fuck them, what about me?'. That's exactly the mentality that allows employers to exploit workers.
To suggest that another worker simply walks out on a job for another is (sorry) stupid, too. Firstly, not everyone has the luxury of such choices. Secondly, the position is only going to be filled by someone else and the exploitation will continue. Thirdly, as long as there are fellow workers with your mindset, even if they both leave, they are far more likely to find themselves working under similar or (as you say yourself) worse contracts.
Zero hour contracts are the modern day equivalent of the charge-hand at the factory gate hand-picking who does or doesn't work today. That practice was abandoned between the wars. It is a ridiculous notion that any worker in 2017 is operating under a worse contract than a worker in 1947. Zero hour contracts are an abomination against workers rights (they've already been outlawed in Ireland (where incidentally the minimum wage is also higher than in a country 20 times its size, next door)). Please don't use them as benchmark for anything other than exploitation.
In anwer to the OP's question, as you may have guessed: yes, yes, fucking hell yes with a cherry on top.