As Wil Weaton puts it, "Don't be a dick." This can be applied to all facets of life - even in the wild jungles of gaming communities. Gaming can sometimes have a toxic splash. At times, the competitive nature of some gamers create rifts, which seem to swallow all semblance of human decency.
This is not to say you should never be competitive while gaming - the drive to achieve victory is inherently fine. It's the whole "ends justify the means" part that can be a bit cloudy. The most obvious example of this is the use of hacks & cheats. This is not only a plain-cut violation of games' Terms of Services (ToS), but it's a pretty obvious moral no-no. Bypassing normal gameplay by thrashing the rules of the game reflect upon your own character - and I don't mean your virtual avatar.
The waters can get a little murky at times when it comes to kindness in gaming. I generally do my best to remember that each virtual representation is not just xxNoobslayerxx, but (botting aside) another human being (let's call him Joe), with their own set of characteristics and issues.
Say you just beat the first boss in a dungeon while running with a random group (including Joe). You rolled on a piece that you and two other classes (inc Joe) can use. Congrats - you won with a 73! Later, you take out the next boss, and another appropriate piece drops.
Do you roll? I mean, you did put in your fair share of DPS - surely you deserve the luck of the RNG. Then again, you just won that last piece, and it looks like the other two guys could really use this one. But...I'm sure Noobslayer doesn't really care - he did kinda mess up on that one trash pull, causing a wipe, and I'm sure he'll just get this piece another day.
Then again, what if Joe (Noobslayer) does care? Maybe he had a terrible day, and gaming is his only daily consolation. Perhaps this is a player's first foray into a dungeon/grouping experience, and they did their best.
While it's almost impossible to know exactly what a player's situation may be, it's always good to keep an open mind and heart about your fellow gamers. If the loot rules allow for Greed (which will put you in a queue to roll for an item after rolling for any that selected Need), maybe consider letting the other two roll first.
At the end of the day, it's your gaming experience, your decisions. While I can't tell you what to do, I urge you to remember that you're not the only cookie in the jar. Don't hog all the chocolate chips, don't crumble others mercilessly, and enjoy the time you have together before we're inevitably devoured by time.
Boy...that metaphor turned grim, though I do now have a hankering for some Oreos. On another note, due to recent events, I would like to add that depression is a serious issue. It can completely alter the direction of one's life, and in tragic situations, may even end it. If you or anyone you know is experiencing some form of depression, please do not hesitate to reach out to somebody.
Links, if you are struggling: