That is not correct. If Congress makes a law that people cannot say the word "Trump" or they will go to jail, SCOTUS would rightly state (let's hope!) that this is contrary to the First Amendment and Congress "shall make no law..."
“If Congress makes a law ...” Yes, as I wrote, the Supreme Court judges Congressional legislation, whether it is constitutional or not. The Supreme Court cannot act directly on Congressional actions, but only when a case is brought into the court via the legal process within the Judicial branch of government.
However, Congressional impeachment is not a law, not a piece of legislation. It is also not a court that is tied to the Judicial branch of government. It is a special right of Congress granted to it by the Constitution as part of the separation of powers. When the House impeaches and the Senate tries that impeachment it is holding an unique type of court which was established by the framers to be the legislative check on the power of the executive.
The Constitution says Congress has the SOLE power of impeachment, but that impeachment is restricted to those holding office as a means of removing them outside the normal election process due to extreme crimes.
I totally agree with you that what we are seeing now in President Trump’s second impeachment is unconstitutional. However, the Senate did not agree that it is - so here we are.