This case
Simply, yes. Gobies--"goblins" can be good. I could be wrong (read more).
Generic rule
You've got to give the people what they want. This is the rule of DMing that I live by because: in any job, the customer is always right, or your boss is always right. I look at the DM as someone providing a service. I'm not saying you should overly suppress your creativity or rely on sensationalism because long-term, people won't enjoy that, IMO. But if someone is adamant that goblins can't be good, you only have two options:
- Accept that.
- Alienate the player.
Each player is relying on you to help her completely envelop herself in a fantasy world. Unless the player is skillful enough to make the dissonance organic to the world in her own mind, and the conflict intrinsic to the champion, you risk awakening the player from the fantasy!
As you go on DMing through your life, you will meet all kind of player, and each player will request a different style of DMing. It's best to always give way to more experienced DM's and to player requests because then, you can get another DM gig, and another, and another, and another, easily: just say "I know that style".
Psychology
- Environment shapes behavior.
One thing students of Psychology learn in their Behavioral Shaping class (save for the students going to hack schools), is that "management" is always stronger than "insight". You can tell a consumer "you have this problem", and you can verify understanding, but it's highly unlikely that this will end in "behavioral extinction". Rather, an environmental change must be made--management.
For example,
- Having a consumer repeat: "I have a smoking problem". - Unsuccessful.
- Having the consumer's family participate in decreasing the number of daily cigarettes over time. - More successful.
Essentially, the environment shapes the organism; therefore, if goblins grew up in an area that nurtured goodness well, it's likely that many of them would be shaped into goodness.
- The evolutionary perspective
In our world, we find certain elements of psychology to be shared between most organisms. For example, if an organism is caused pain, it almost always reacts with violence. But as creatures become more intelligent, they become better able to control themselves despite antecedents.
Since Freud, and perhaps before (i.e., since the writing of Pandora), Psychologists have believed that humans have "evil" implicit behaviors. For example, from Freud, the Oedipus complex, and its counterpart, the Electra complex. It is also believed that we are naturally 'prejudice' towards those who look different from the ones we grow up around (due to the nature of our attributions of behaviors to prejudices).
That said, why shouldn't an intelligent organism such as a goblin be able to overcome its implicit desires/urges?
Background that says 'no'
The background info I find that says 'no' agrees well with the above. You can see, in
- Token: Goblins are often thought to symbolize the Nazi's--these were people brought up in an environment that nurtured evil. What can we blame other than the environment? We cannot blame humanity because we have not all done such atrocities. We cannot blame race because not all Germans have done such atrocities. Ah--we've already mentioned everything that can be connected to goblins (species and race). And this is really where DND goblins come from.
- Grimm: Goblins are the ghosts of the haunted forest, a force of death, and/or a devil. In the first case, 'haunting' is supposibly evil; in the second, 'a force of death' is one whose job is to cause death--causing death is evil; in the third, a devil has a purpose which it considers good, though most consider the purpose evil. Only in this last case can we assume that a goblin is beyond being good. This is the nature of taint: an affliction that ultimately leads to a party member's loss due to her becoming irreversibly evil.
Personal applications
I created an orc, adopted by monks, whose dream was to become a paladin. Although many spurned him with dry looks and unfair treatment, he had been trained since his adoption that the strength of his anger was an indication as to how much he must give himself to his deity and use his mind to overcome violence. The players really connected to him, and he was really really great for a hack-and-slash in Ravenloft. He went well with his Drunken Master mate, Rogue wife, and Archer/cartographer university adviser. It made for a wonderful story, too.
*But remember, there are always times it will be inappropriate to surprise a sensitive player with an out-of-the-ordinary combination like this! If you get complains, I recommend going with popular or other-participant consensus!