Let's say you are an old school middle aged person who has never used the internet much. One day you decide to check it out to see what's the buzz all about. Unfortunately for you, you stumble across total cesspits like 4chan, reddit, Daily Stormer and all the rest. You form an opinion: the internet is full of toxic people.
Then a group of white knights comes screeching at you, "NOT ALL INTERNET USERS ARE LIKE THAT". Yep, not all internet users are like that. Fortunately for you, you have been on the internet for decades and know how to correctly identify and avoid shit like incels, 4chan etc. A person visiting the internet for the first time, however, does not. It is not their duty to be super knowledgeable from the get-go and form the correct first impression. They see several toxic subgroups, they decide that the entirety of the internet is toxic and you can't blame them for it. The internet, on the other hand, should have collectively cleaned up its act and gotten rid of its more toxic elements in order to make it more welcoming. Habitual internet users in this case don't have the excuse of ignorance.
Let's apply this to other groups.
A white person complaining about black gangbangers and gangsters can claim ignorance. The black community, however, knows that there are both black gangbangers and completely well-adjusted black doctors, engineers, scientists, office workers, movie-makers etc. The black community, however, cannot claim ignorance and disavow the gangbangers that are a part of their community by making statements like "NOT ALL BLACK PEOPLE". It is a community-specific problem and it should be fixed by said community.
A woman complaining about fuckboys from the local frat can claim ignorance. Men as a whole, however, know that there are both fuckboys, incels, mgtows and well-adjusted, totally sane men. Men, however, cannot claim ignorance and disavow the fuckboys that are a part of their group by making statements like "NOT ALL MEN". It's a group-specific problem and should be fixed by said group.
Same goes for a lot of other groups and their specific problematic subgroups:
Women and gold-diggers.
Americans and Trump voters.
Muslims and Jihadists.
White people and far-right KKK / Nazi groups.
If you belong to a certain group, it is YOUR duty to clean your shit up. You can't expect other people not to develop feelings of hatred towards you after being exposed to the less savory subgroups of your group. They can claim ignorance. You cannot.