How is an extramarital affair an impeachable offense?

It's not so what are you babbling about? Do you even know? Then again a dishonest, biased Congress could make it about about anything they really want it to be about.

Adulterously sodomizing an intern under your power in the Oval Office and in the Presidential Chair itself is an egregious violation of personal conduct, which easily falls within the clauses describing 'high Crimes and misdemeanors' which are defined as personal offenses which, upon public revelation, could measurably damage the public good or violate the public trust.

How?

The act is a grave moral offense because it violates the institution of marriage and moral public example, is an act of sodomy, (once even openly outlawed as morally reprehensible), is an act of blatant disrespect to the office itself, (especially given the intentionally chosen location and its historical significance), is a serious violation of standards of workplace treatment of subordinates, (even if consensual), opened the office itself up to potential extortion or corruption, and eventually did result in actual perjury and obstruction of justice.

It's not. However, lying about it under oath in sworn testimony given as part of a sexual harassment investigation and then actively interfering with said sexual harassment investigation to cover up that you lied under oath is, the impeachable offenses being perjury and obstruction of justice.

It is not.  But lying under oath in a court case is perjury.  That should be impeachable.

It's adultery, so it's not personal. It's adultery ffs. That, in itself, makes someone a victim, which takes it outside of the realm of personal.  

It's bad, but it's not a crime.  Are you talking about B. Clinton?  He was impeached for perjury, not adultery, as far as I remember.  He was disbarred in at least one State because of it.  And he has credible accusations of rape too, not during his presidency that I know of.  But he had too much power to be charged with rape.  

When you are doing illegal things to cover it up. But How  many affairs is too much for you ? IF   is that many  would that idiot be susceptible to  a spy?  I prefer my candidate to think with  the slightly bigger head.

Biden never has affairs. Just feels.