Blood like that could be minor, or not but not necessarily alcohol related. I think the ignoring it and not getting it looked at is alcohol related... Some of us like to bury our head in the sand and hope the problem will go away.
I chimed in here to let you know that I had a similar problem, after getting sober, I saw a GI and after a colonoscopy was diagnosed with ulcerative colitis. Since changing to a vegetarian and gluten free diet, I'm in remission at the moment. Like Lexie said above, the scary blood is the dark tarry blood, but he needs to get checked out regardless.