Even if you grant the idea that a person working at MTurk is just a normal person, which personally I doubt. You have to contend with both the fact that they're highly likely to be lying about their identity in order to maximize the number of tasks they can be included in, and they're also likely giving trash answers in order to complete the survey as fast as possible. I spent a bit of time doing mturk for a while, and it was absolutely one of the first things I started to optimize - "How do I get through this survey quicker". It's incredibly difficult to earn minimum wage doing mturk, which brings us back to the idea that it's unlikely it's just an average normal person doing it.

It's absolutely possible to produce a rigorous statistical result from the data, but that's useless if the data is all lies.