And, I'm sorry, but can we please, please not get offended by everything? There are probably a multitude of reason why Larian chose it, or there might just be just one. Perhaps the voice actors for the goblins got together and just decided that the accent was appropriate. Who knows. But to be honest, I enjoy hearing them speak. For whatever reason there may be, it sound right to the developers. Larian doesn't mean anything by it, they are not trying to offend, or poke fun at anyone. It just sounded appropriate to them for whatever reason.
The goblins speak too much. They're supposed to be monsters you can kill without moral contradictions. They are too clean and groomed, especially the women with their hair-do's.
You are referring to the "old way" of viewing monsters in D&D in general.
I too come from the AD&D days, where evil was evil and of course, must be smited by the heroes, at whatever cost. Where goblins snuck into towns and villages, stole and then ate babies of the "goodly races". Now, it seems we have to sympathize with them before we cut them down.
I will admit, it does add a bit of drama to whole RP experience. It has its pros and cons.