Justifying your low GPA, a double-edged sword?

I took a look to the online application form from LBS, and there's a question that says "Do you feel that your academic performance so far gives an accurate indication of your potential for success at London Business School? If so, why? If not, why not?".

The first thought was 'great, I have an explicit blank to talk about my GPA', but soon I began to think of the interpretations that AdComs could make up, for instance:

1) Suppose that in your university courses there were quite workships based on teamwork, and that you did those with your colleagues, who didn't care too much of their grades (not everyone wants to do an MBA). Usually, despite your extra effort, the grades weren't as high as they could have been, because your colleagues didn't helped much and always waited till the last week to start working.

When I try to be in the head of the AdCom, I can see this from two opposite points of view,
1) Seems that the candidate had to do a big effort in order to compensate the lack of motivation of their colleagues.
2) Seems that the candidate lacks of leadership, since he couldn't motivate his colleagues to do a better job.
and so on..

It is just an example, but what's your opinion? Is it better to try to expain or is it better to be quiet so you don't make it worse?

*BTW, my gpa is 3.1, I know an application depends on the whole thing, but do you think is enough for LBS, so not to be waitlisted at first glance? (Thanks!)