That's why I used "scold" - no matter how politely you try to do it, most people don't take kindly to being criticized about their driving/cycling by strangers, particularly when it requires being stopped by said stranger. They will feel like they're being scolded. And they will probably respond in kind.
And if you cannot speak up, then why complain about it? Think society only works if there is some level of checks in place if you're behaving nicely. And that should be done by people, not police.