This is a legalistic argument. It's based on the idea that if it's legal it must not be bad behavior. By that logic, Trump's attempt to get the Ukraine to launch an investigation against a political opponent by threatening to withhold aid isn't bad behavior because it wasn't a crime. Of course it was bad behavior. A politician can act absolutely horribly and it not be illegal.
Pelosi's tearing up the speech was absolute nonsense. Was it on the level of other things that have happened over the last several years? No. However, it was a highly visible and absolutely ridiculous act. Same thing with Trump refusing to shake hands. It's so petty and ridiculous and serves absolutely no point.