When you start talking about the line between "good" and "evil" in role-play you're potentially opening up a can of worms because people enjoy debating it. Largely because they can come in different varieties.
In my role-play experience and with most of the people I've ever role-played with, the line between "good" and "evil" can be very easily blurred and comes down to two things: intent and perception.
Intent is defined as the purpose and will behind an action from the mind of the actor:
"Evil" often has intentions inconsiderate of the cost or affect on others. "Good" often has intentions considerate of the cost or affect on others.
Both can be selfish but only one tends to be selfless.
Perception is defined as the purpose and will behind an action from the mind of the audience:
"Evil" is often perceived as malicious, extreme, unnecessary and/or harmful. "Good" is often perceived as benevolent, compassionate, sacrificial or just.
An act can be "good" to the actor because he understands the full context of the situation but still be perceived as "evil" to the audience who only understands the moment. An individual's 'alignment' is best determined by the sum of both intent and perception.
In terms of this game, the "good" character isn't going to start a fight if it can be avoided unless more "good" can come from the fight than avoiding it. (Such as fighting the establishment that is inherently preying upon others). That same character won't hesitate to defend themselves if attacked because there is nothing inherently evil about defending oneself.
