OK, not that I'm sure what you mean, but if you're asked to give marks, from lets say 1-5, why wouldn't people would be allowed to give low marks if they decide to mark all pictures?
Getting a bad review, or a critical comment can be a way to learn things. It doesn't mean people are rude.
Being a reviewer myself I know that low marks hurt, but it is also a way to change, if you get many low marks for one thing and very high marks for another. Best is of course if people comments why they give a low mark, then you will defineately learn from it.
Also being part of a few photo competitions, I've learnt a lot more from the photo's that didn't end up among the top 5 than from the ones in the top 5. That's because people comments and gives me a reason why they don't like my photo's. Sometimes I learn from it, sometimes I just ingore it, people don't understand my way of thinking.
So, my suggestion is: don't take it personally, it's just a mark. You don't win anything if you get high marks.... and you don't learn anything with too high marks.