There have been a few cases where images of MIB have been captured on video. The witness reports support the theory they are not human beings, but alien entities in disguise. Sometimes, in poor disguise. Sometimes, almost comical in appearance.
But, there is nothing comical about being threatened, bullied and intimidated.
We live in a society that prizes the right to speak openly without fear of being silenced with acts of violence. There’s no evidence that MIBs have ever harmed anyone, other than to frighten and intimidate.
MIBs could be alien entities operating with the government’s blessing.
The alternative is that they are acting independently and world governments, shadow or otherwise, are unwilling or unable to prevent MIBs meddling in human affairs. The latter is more likely.
Could MIB actually be responsible for abductions and missing person cases? There are a lot of people every year that simply vanish into thin air. The past ten years has seen an increase in the number of people that go missing. Each year reports more cases than the previous.
If you’re interested. check out People Are Vanishing Into Thin Air, In Our National Parks. It describes the inexplicable disappearances of people from state and national parks.