"Running away from a fight".  That term always amuses me. 
First off, let's define "Fight".   
If by fight you mean a fair confrontation, then no.  Unless I'm out of ammo- then I'm on my way home anyway and just have a small detour.  
But all too often those accusing people of "running" are expecting a P-51 to get into a co-alt turning brawl with their Niki's and what not, and are just sweetying.  
Basically, it comes down to this- I'm not in the game to get shot down.  I'm in the game to shoot *you* down.  If I come across a situation in which I don't feel I have a significant chance of victory, I retire and come back with more of an advantage.  
Jumping into a fight in which the best chance you have for victory is for the other guy to make a big mistake doesn't seem smart to me.