I always try to be respectful in game, to both allies and opponents. Sure, I can flick the rage switch here but I always try avoid direct personal insults just incase that person may be mentally weak. You never know if that person on the otherside of the screen may be suffering from major real life issues and your anonymous harmful words may be the pivoting action that makes them a tragic mistake.
I bet if you knew someone personally that was suffering from depression you would do anything to try lighten their load and get them to view the world in a positive manner again. However, you could decide to further bring them down by adding in more abuse, causing their condition to further spiral out of control. I think when it comes to the internet, people are more inclined to pick the later option as they simply do not know the other person.
A guy I used to work with in high school chemistry class ended up killing himself. He wasn't a close friend, just a guy I knew and worked with and I wasn't aware he was going through a rough patch for couple months til after he died. I suppose all the issues just compounded on him and he took that choice to get out of it. I knew something was wrong with him a few hours before he commited suicide, but I did not realise the magnitude of his issue. I just let him sit there and relax, whilst I did all the laboratory work. Even though I never contributed to his problem, I've always wondered if maybe just some nice words from myself would of made a difference.
In context of the internet game, although you would never find yourself directly involved in such a predicament, you can still be indirectly be minor contributing factor to someone harming themselves. After that experience with that guy in my chemistry class I just assume everyone has depression issues and I try to not contribute to their problem but fix it. On the internet just staying silent or being positive is the best thing you can do to achieve that.
It doesn't hurt to just be nice.