And yet they covered it up.
See, there you get into the gray area between what's legal and what's moral. Watson acted to save Holmes's life, but under the circumstances, it would be difficult to prove that to the satisfaction of the police and the legal system. Thus, Holmes did what he often did in the original stories -- placing what's right (in his judgment, at least) above the strict letter of the law.
No, this was plainly presented as Red Herring followed by revelation. We were led to assume that he was suffering from PTSD, but then were given the character insight that this healer thrives on war.
I wish you'd stick to the facts instead of twisting everything. It was never shown that Watson thrived on war. I mean, come on, it's ludicrous to say he thrives on war when what got him over his psychosomatic leg pain and trembling hand was chasing a cab through the city streets. Does that constitute warfare in your book? No. That's rubbish. We were shown that Watson thrives on excitement. On adventure. On danger. "I said dangerous and you came anyway."
Moffat has said it himself -- "Other detectives have cases, Sherlock Holmes has adventures." The point was to show Watson as someone who craved adventure and excitement, to show the two men bonding through shared adventure -- much the same way the Doctor bonds with his companions through shared adventure.