At what point can you no longer express controversial opinions without being called a loser?
It absolutely is. "MRA" is a short cut to dismiss an entire spectrum of arguments and perspectives. Just as farcical, but on the opposite side, are people who declare anyone who has a problem with something like, say, "GamerGate", a "SJW".
These are shorthand for idiots. It lets you pretend that you're in a tribe and everything is black and white.
And to provide a sentinel value for the previous search space, I'll just say it. You, and everyone else who may be wondering if someone on the network is calling them a loser, are all losers.
Now that's taken care of, and you can go about your business, expressing controversial opinions without worrying about incurring greater harm to yourself than has already occurred.
http://en.wikipedia.org/wiki/Elephant_in_Cairo
Don't despair. Being called a loser does not make you one.