I agree with the first half of that.
However, as for the second half, I don't think (m)any on here are really saying that a person must definitely be 100% innocent if they're found 'not guilty'. Everyone is aware of the burden of proof, miscarriages of justices (both ways), etc.
I think most are just responding to the initial reaction of some that implies, if not states, things along the line of 'another rich guy gets away with it', 'there's no smoke without fire', etc.
That's the kind of Trial By Media / Court of Public Opinion stuff that is very unfair. If the court - who had all the evidence to examine - failed to find / prove the person guilty, then that should be the end of it unless the court re-tries them. People still saying / implying 'they couldn't prove them guilty, but they're still probably guilty of it' - and that stigma following them around, with the not guilty verdict coming with an asterisk, is where I think the big issue lies with some, and why they say the person shouldn't still be treated and talked about as if they were probably guilty and just got away with it when no-one actually knows that.