Not sure about the details, but I thought that due to the fact that pld only combo is their enmity one staying in sword oath is better. With proper use of shirk both tanks should be able to stay out of tank stance. I do not think this is an issue of a so called "moron" more so someone trying to fit within the moar dps mindset and maybe not executing it properly. I know of many tanks that try to tank in DPS stance without proper cooldown usage due to people telling said players that tanking in DPS is the proper way to tank without being told the added context. As I said not sure of the details but calling said player a moron seems rather silly since people are often told to do something especially when it comes to the proper way to tank and heal without the context so they simply just blindly follow the advice and thus share same advice with others. Granted he may be a mentor, but that is simply a meaningless icon / title.
In the end said player information was right, just poorly executed.