I liked to solve the problem of a Warlock-not-Evil by taking the
Fey Heritage feat, and RPing the warlock powers coming from this Family inherited bloodline.
Considering this is the first line of the NWN2 wiki description for a Warlock:
Born of a supernatural bloodline, a Warlock seeks to master the perilous magic that suffuses his soul.
This is also from the Culture of Warlocks from the Forgotten Realms wiki:
Like sorcerers, many warlocks came from a supernatural bloodline, and it had been said that warlocks were "born, not made." This was not true for all warlocks, though many did indeed come from fiendish bloodlines. Those that weren't were still often touched by destiny in some special way, sought out by powerful extraplanar forces as tools and minions, altering their souls and giving them supernatural abilities beyond the ken of most mortals.[6] These forces beheld warlocks to their power, though some broke away from the chains of their servitude to forge their own destiny.
What I personally think is the key to a Warlock of any Alignment, is that it is a Character always in conflict with the power they wield, be it born into them, or made through a Pact (of whatever reason).
And, I think THAT is the most interesting part for you and for others to enjoy, in the Role-play you bring to the Server.
That said, one always need to keep in mind OOC that many other Characters have IC reason to make all sorts of one-sided judgements, either hugging or hating, on the spot or through time-to-get-to-know-you. And, I might add, a Warlock is really a High RP type of Character that needs some serious investment in type, not just a laissez-faire "I like the power play" attitude of the Build.