I've got a German passport, grew up in Spain, live in Kenya but spent most of the last decade almost exclusively speaking English...
With that out of the way I must say that I do not have the impression that most people who come across as aggressive are being misunderstood because of their poor language skills. Yes, maybe not everyone shares the same sensitivity for NSFW language as it is fostered especially in the US but, most people who rant about stuff are doing just that; feeling empowered by the anonymity supplied through the internet they loose any blockades society imposes on tactful behavior and set their rage free, often acting as a valve for other frustrations in their lives.
That said I actually haven't had the feeling that this is often the case in this forum, in fact to date this is the most tolerant and so to speak 'cleanest' forum I am aware of, if it was to turn into a problem you could force people to display their real names as it is done in other forums (Phillip Bloom's forum f.e.), but then who knows, maybe one day Canon will decide that what we are doing here is against the rules and come after us...