I have never heard that before. I always remember hearing "as long as it is bled properly, then you can eat it."
I just googled it and found this:
By Dr. Mercola
The red juice that often collects in a package of red meat is not blood, as many assume. Most of the blood is removed during processing and any that remains is usually contained within the muscle tissue.
The red liquid, instead, is a mixture of water and a protein called myoglobin, whose purpose is to help ship oxygen to muscle cells. Myoglobin is deeply pigmented, which is why the more myoglobin a meat contains, the darker (or redder) the meat will be.
From http://articles.mercola.com/sites/articles/archive/2014/10/25/myoglobin-red-meat.aspx