I've already quoted from the rules a few posts above, and stated that precisely because there is not a clear standard, the situation can be called either way. I haven't even said what my opinion is in this scenario, just that the ref should have at least viewed it himself (again, as recommended by the rules, per my earlier mssage)! If your argument was "Royer is not clearly obstructing Guzan's vision," I'd agree that your argument is reasonable. Although, again, others may disagree, and make a decent argument the other way.
Unfortunately, your argument was "no one is offside unless they completely block the keeper from seeing" and it has now apparently evolved into "AND they also have to be right next to the keeper", judging by your comment that Muyl is not blocking Guzan's vision in the snapshot above.
Anyway, made my point, don't think arguing it further with you would result in anything productive.
You are right, I stated my opinion based on what I observed in many the years of watching soccer in multiple Leagues as the rule is open to interpretation. Note that the rule does not even say interfering with the GK, but with the play. I have not seen many instances where a player 8 yards or more away from GK is called for interfering with the play blinding him. I have seen this called plenty of times when a player is pretty much right next to GK blocking him completely.
So, I stated my opinion, and you chose to attack every sentence I made, including the one where passive offside was not called to have more goals, without providing any evidence to the contrary. It's fine if you disagree, but you seemed pretty aggressive attacking my opinion, so I would expect to see some sort of evidence that I am way off here. You provided none. You just stated your own interpretation of the rule, which hardly justifies the attack on mine.