Do you think they exist, are they real government agents, are they hoaxers, or are they just in the imagination of to those claiming to have seen UFOs.

No more real than the cast and characters of the film series and book with the same title, what do you think?

What do I think? I have not seen the MIB movies which I understand are complete sci-fi.

There is a belief that there are Real Men in Black, out to suppress and prevent compelling evidence and information in relation to UFOs being made public. These are the ones I was referring to which I should have made clear when asking the question, "Do you think they exist, are they real government agents, are they hoaxers, or are they just in the imagination of to those claiming to have seen UFOs."

I do think some aerial phenomena create these
illusions of UFOs. Strong enough for some people to interpret and believe they have seen a UFO, but I do not believe it was a UFO they observed, so I do not believe Real Men in Black exist.

Yet some believe there existence is the reason why no proof of UFOs exists in the media.

In the U.S., any reason seems justifiable,
to create new government organizations.
Mostly, for the empowerment of the fools
we elect to high office.

I've no doubt, more than one federal agency
exists under the guise of an MIB like structure.

There has been eye witnesses to sightings that described the government officials who questioned them as dressed in black. The government has admitted that the Majestic 12, Project Bluebook, and a few others were real at one time and released the documents to prove it. I suppose dressing in a black suit and tie would be considered proper for that job. MIB as a organization I doubt it but people dressed that way to do that job yes.

There has been things said in some UFO investigative TV programmes, of men in black advising those having had a UFO sighting not to talk about it. They appeared so quickly after their sighting they wondered whether these men were in some way connected to what they believe they saw, even to speculate if indeed these men were human. All the more mysterious, did this really happen in the way they described it.

I've never seen one/any,
but I believe they exist...

I have Men in Black coming to My Home, Looking for Me. I'am a Resident Alien.
They Work for the Government, but it Turns Out they are IRS Agents.

When watching the docu series "The Alaska Triangle" people tell that real men in black turn up whenever people have clear evidence of UFOs or aliens. These men in black confiscate the whole lot, albeit photos or vids or sound material, and make sure you never ever talk about it or else...
So yes, it seems they do exist.

I think the saying 'no smoke without' fire applies to all of these things. In this case the MiB movies are the smoke, but there are a lot of things in that movie that are considered truth by certain people. The one(s) who made it wasn't a knucklehead.