The problem with EA and other utilitarian systems of thought is two-fold. Firstly, you can't predict the future so really you're working off your biases. Secondly, unfettered by principles other than the end justifying the means, you can easily turn those aforementioned biases into justifications for committing horrible acts. Mass murder, or evidently, theft on a massive scale.
For instance:
"The technological revolution was a disaster for the human race... so I'm going to murder a few people to draw attention to my manifesto against technology."
"Social inequality is a disaster for the majority of my countrymen, so I'm going to murder the Bourgeoisie"
"My altruism is more effective than anybody else's, so I'm going to steal everybody else's money so that I can put it to better use."
How do you stop this shit? Deontological ethics. Don't murder, because murder is wrong. Don't steal, because stealing is wrong. Damn the consequences, stick to simple principles such as these.