That's very true. However it does not make me wrong. The way I see it, if someone was reported for the same thing over and over again for something, it will eventually be punished. Not because Riot saw it for themselves or they have evidence supporting it but because enough people reported it. If these people who were banned didn't say anythign but were trolling in their actions, then either a Rioter saw it for themselves or people reported them enough times. I highly doubt a Rioter saw the actions done, so it has to be the amount of people who reported them. If enough people report someone for something, then clearly they're doing something wrong so something must be punished.
Now, with that in mind, if enough reports is able to punish someone who's doing something that can't be seen by riot but there are many people who don't like this person for some reason, this would hold true to people who don't do anything wrong. You have many people out there who report people out of spite for a number of reasons. Someone was crap, someone didn't say anything, someone left you when you wanted to engage enemy, whatever it was you didn't like them. You can send a report and it's on that tally that's on every account. If you keep getting in matches with people like these, that tally gets higher and higher. Eventually it would reach a point where Riot notices. They'll see that tally mark and think this person's doing something wrong. They may not know what was wrong, but it's something that's upsetting enough people. So then they punish the person simply because enough people were upset with this person for doing nothing wrong other than just being there.
Now, with that said, this works both ways. Riot 2-week banned me for "self-deprecation" 4 months ago. 1 month ago I was declared reformed and rewarded with loot. In those 4 months after my ban I did nothing different and I'm still doing the things Riot temp-banned me for. They know full well that I'm still the same I was before, but they continue to reward me. I'm a classic example now that Riot is rewarding bad behavior while punishing good behavior at the same time.