For women and other non-male genders, the worst thing ever is when men do their classic mansplaining, usually about things we already know plenty about. Some of the things men try to explain are truly ridiculous. Here are some of the worst instances of mansplaining, as told by the women of Reddit.
u/Pipcy asked: Women of Reddit, what's the most ridiculous thing a man has ever tried to explain to you?
What the hell....
I once got into an argument with a man online in an ancestry group. I happened across his attempt at mapping a family line of mine (mother's side, so I have a different surname with a completely different country of origin), that also was somehow connected to him. He was livid when he saw that one of the people in this family line was recorded as having died in New York, when everyone knew she lived in San Francisco her whole life and had no family recorded in New York. He went ahead and made a public correction to the family line, while grumbling about how people really need to check sources.
When I corrected him, saying that she really did die in New York, while staying with her daughter and her daughter's family, he so kindly explained that I was a f*cking moron.
Except I was there when she died. In New York. She was my great grandma, I was a preteen at the time, and he absolutely refused to believe me, even going so far as to claim I falsified her death certificate. I legitimately can't figure out why he was so emotionally invested in her and to this day my family and I have a running joke where, when anyone goes anywhere (the store, vacation, work, etc.) we feign anger and shout "CHECK YOUR SOURCES, MORON!"
Ewwwww.

Why younger women need older men in their lives to teach them about sex, as it helps them "blossom into a flower." I was being groomed into having sex with my mom's then-boyfriend. Bastard even set me emails to articles that "proved his point" and links to books as well. He'd known me since I was 14 years old. I had just turned 18.
This is just laughable.
That I only got my period during the full moon. I tried explaining that werewolves and women are different but he insisted for a good twenty minutes that he was right, ignoring that fact that I'd been getting my period for years and he still had yet to get his.
That brings a new meaning to that word...
This guy tried to explain to me once how a penis has a bone in it. He was being dead serious, and I was confused as to why he thought that considering he has one. Regardless he didn't believe me when I told him there's no bone.
That's just ignorant.

That the pain of childbirth is a myth and women have "learned helplessness".
I asked him, oh are you an OB/Gyno? Nope. Are you any kind of medical professional? Nope. So I say, why do you believe that millions of women in all parts of the world are just pretending that childbirth hurts? He says "oh I saw this article online and the title was about" which is when I interrupted him to say "you didn't even read the article? You saw a headline and immediately believed that over the experiences of every women who has given birth?"
I was about eight months pregnant at the time and basically lost my sh*t.
What's with guys thinking they know so much about periods?
Periods stop when you lie down.
Yeah champ, that's why they market pads specifically for night time. We sleep standing up like some robot I guess.
Why do so many men think this?
That I pee out of the same hole from which I push babies.
On and on we went, me providing increasingly detailed delineation of female anatomy, him shrinking physically and verbally 'til he just grunted, slack jawed, and walked away shaking his head. He was a man in his 50s.
Now THAT'S cool.

At an airshow, two guys tried to explain to me that there were no women flying military aircraft in WWII, and why they didn't have the right "temperament" to fly those planes.
My mom was a pilot in WWII. Oh, what a FUN day that was!
Uhhhhh....
I will never forget this incident, in the 9th grade my high-school school health studies teacher tried to explain to us how tampons and periods worked.
This man looked us dead in the eyes and said "Yes, the cotton will absorb the sin that you bleed but it will also make you impure and your future husband will be unsatisfied with you." That's private Catholic schooling in the midwest for ya.
I think I'll start calling my period my monthly sin now.
Talk about mansplaining.
What an americano was. While I was making it. At Starbucks.
Then I proceeded to tell him the history of it and he tried to argue that it was French, not Italian.
Obviously it's American. It's even it the name!