Never ever ever ever judge anyone for doing something, there is no sense. What you do, or I do, or they do at the end of the day does not affect you or I unless they are hurting someone, then you step in.
Don't like the way people are dressing up or playing? You should then question your logic or feelings because it's just dressing up and does not affect you in any shape or form.
As for the seriousness of the game, it is just like was mentioned. In every sport, soccer and hockey for example, there are casual players who just wanna get some exercise and there are competitive players who strive to be better and COMPETE. Same rules applies to airsoft, it is NO different.
Again if you are questioning others, I would question your insecurity because it doesn't matter what they are doing, only matters what you are doing, and if you are happy with yourself, you will never worry about what others are doing.