I think people who complain about someone using a top tier character just have a different mentality. When you go to a competitive event, you should probably be at a position to do good, so using a top character (especially with money on the line) is a no brainer. But sometimes people need to own up to that. There are plenty of players who picked someone up because they wanted to play a tourney viable player but then tried to make up some story how they always liked that character and it was just a natural progression. Bullshit, if you do something at least have the balls to own up to it.
Same goes for those who play bottom tier characters, either because of character loyalty or some other factor. If you use a bottom tier character in the tournament, you give away your right to complain how he is bottom tier and how you lost because your opponent had better tools. You know why? Because you went into it fully aware and you don't get to use your excuse. If you want to be competitive, adapt or STFU.
There is nothing wrong with wanting to win, especially when you play competitively. Play whoever you want in casuals, have fun with it, show your character loyalty or what not, but when money's on the line, and you know it is, it's on you to chose who you want to play as and so are the consequences of that. On. You!
I was lucky enough because my favorite character in MK has always been Kabal and no matter what I'd be using him on some level or the other. The cards just fell the way they did. Same goes for Sonya, who I was in love with ever since the first movie. If they weren't top tier however, damn right I would pick up Lao, Cyrax or Kenshi for tourneys. I also happen to love the design choices for a lot of MK roster, so in casuals I used to play Shang, Stryker, Kano, Liu Kang, Skarlett, Reptile... A lot of characters, would I bring them into the tourney? Hells no. Would I play them in casuals for fun to explore the match-ups an the meta game? Hells yeah.
For Injustice, I know I will try all of the characters on the roster at some point. It will happen. I also can tell that I will play Flash and Sinestro no matter what in casuals (also Harley for sure) and in the first couple of tourneys. When the tier list solidifies however, and if my chose characters are not on it, I will definitely pick up a character that is close to the top (if I plan to keep going to tourneys).
I think there are two different mentalities between casuals and fair play and tournaments and people have trouble switching their mindset from one setting to another. If you want to be a competitive player, you have to learn to do that or stop complaining about others who do. At the end of the day, play whoever you damn please, but don't blame other's for your choice.
lol
) and in love with all this meeting new people and seeing new places and "leveling up" as they say. I don't need to win or even place well. Yet.. 
