If they were one shot (or less) behind the group ahead and keeping up with that pace... If I was in that twosome I'd be thinking I'm not holding you up as long as a close ranks on the 18th. I'd also feel that I have no obligation to push the group ahead, that is not part of golf ettiquette nor is it my obligation. That is what the Marshall is for.
When you asked to play through I would have let you as I don't like to be pushed and would have been annoyed as I was keeping pace. You shouldn't have called the Marshall on me you should have called the Marshall on the group ahead of me.
(What I would have done as that twosome when you almost met us on the tee box at the 200 yard par three, I would have called the pro shop and said, "the foursome ahead is playing slow and we have two groups backed up on the tee box".)
Why would that matter? I'm a righty player with a dominant left eye. I'll give it a try although keeping my head down isn't really an issue for me. But wtf, I'll give it a shot. Thanks for the tip @spider!