Factually, you're the one who is wrong. Unless, of course, you believe that alleged treasonous behavior, accessory to murder, etc. is suitably punished by being unable to run for elected office in the future. That's the only punishment Impeachment can impose on a former office holder. It's just politicians politically punishing politicians.
Fact remains, if inappropriate political behavior is the charge, political punishment of a former office holder is petty and weak as well as being incredibly expensive, but that could be the motto of Democrats - "vote for us, we're the party of petty, weak and Incredibly expensive ideas".
Congress shouldn't be the one punishing the wrong doing of a former President - the courts should do that - as they did to President Clinton who, once he left office, was stripped of his law license for a period of time for the crime of committing perjury. Your country has three distinct branches of government and the competent branch to mete out punishment for such wrong doing is the judiciary. But you know, as well as everyone else on the planet, that there isn't a court in America that, would convict President Trump of the crimes he's accused of in the impeachment article. And thus, the only way Nancy Pelosi can get her pound of flesh for Trump calling her the fool she is is by rushing through impeachment and unleashing the clown show we're now witnessing.