Good for him and shame on the assholes taping and laughing. We don't get to see what they look like. For all we know they could very well be just as out of shape or at the very least unable to keep up as he was able to do.
I don't see a problem with an overweight man wearing speedo's while working out. He's trying to improve his health while wearing something comfortable. I fail to find the humor. Infact if we find the site so offensive we should ban speedo's for everyone. I admire a man for working out to improve his health and having the confidence to wear something that's not been deemed unfit to wear in public.
Fat European men regularly wear speedos without shame or irony in the U.S., so why wouldn't they be confident wearing them during a poolside exercise class in Brazil, Egypt or even Dubai where the class is obviously being held? At my absolute heaviest I'd be that confident there too.