In the last few weeks I have had conversations with 2 different people that thought any 45 ACP pistol is a "1911". One of them is a pretty good buddy. I was so stunned I didn't reply with much than "are you serious?"

How would you respond?

I don't bother responding to comments/people that dumb.  Might as well try to have a conversation with an amoeba.

It may have been the first Pistol chambered in .45 but not even sure about that?

If they were buddies then something like lol no.

Explain how 1911 got it’s name from the date the military adopted the Colt government model as its service pistol. And how the Colt government is not a Glock 21

I may have you tied for stupid. A coworker and I went to a restaurant for dinner and she ordered filet mignon, when the server asked how she wanted it cooked, the answer was "you cook fish all the way through". The server tried to explain filet mignon was a steak. The coworker accepted it and made one comment when it arrived "the server was wrong, its supposed to be fish", then ate in silence.  Two weeks later we worked together again, same restaurant, same request for filet mignon telling me that the server two weeks earlier was wrong...I had to bite my tongue. Same thing over again how you want it done, yadda yadda yadda. I was so embarrassed.
Now to tell you the rest of the story...she was a college degreed science teacher in a major city high school, left there, and became a ranking supervisor at a major city police department. Go figure....

Oh Lordy....

Not everybody is a gun person.  But everybody is a food person (I would hope).  Maybe she was thinking of a Filet-O-Fish.

Tell them they are reported!!

help them out, more knowledge about 2a and 2a stuff is good

I had a similar conversation with a coworker. He wanted to marry another coworker. I questioned his sanity. He asked, she accepted. They have been married over 40 years.

Hand them a CZ-97 and watch the brain implode.

There was a time when referring to a ".45" meant a 1911.  This was common usage in the military until the mid-1980s and perhaps longer.

This all started when he referred to his  SIG P220 in 45 as a 1911....

Glock 40 problem solver syndrome?

Yup, that would explain your comments.  Some folks just aren't "gun literate".