First of all, everyone has different point of views.
Well it's not wrong to think this way. It's his point of view that everyone should play the gender in their real life in games, especially with soical MMO like this. People take social/dating MMO seriously because they want to find love and such. It's pretty understandable but what if there are MMORPGS that has mono gender ?, such as Elin, Popori and Baraka in tera, they don't have second gender. People can't follow the real gender thing.
There are no limits to which gender you should play. For example my sister, she plays both male and female. She have a lot of fun with it. There is nothing wrong with playing opposite gender unless you want to troll somebody and give them false information, that is just wrong.
I'm not saying who is right and who is wrong, it's just the way you look at things. It is like looking at clouds, people may look at the same exact cloud but imagining it differently, such as green tea leafs ,fluffy cotton candy and etc.
I hope this helps, if not....................... Cookies and soda for everyone

Guhehehe.