Re: Why the hate?
A quick scan of the linked article suggests to me that the incorrect information was itself and was inserted in articles that were of little consequence, who cares if the Buddha turned someone into a goldfish or whether or not a legend exists saying he did.
This seems to be the core quote:
Had I not attempted to unravel my deliberate mistakes, I am quite sure that Wikipedia would still say that the Sagami Railway in Japan was initially set up in 1917 to transport corn and fresh spicy shrimp (can you imagine the odor?) along the Sagami River valley. Likewise, a letter from Abraham Lincoln to Edwin Stanton would still be falsely directed to Albert E. H. Johnson. And the legend of Bodhidharma turning a bridegroom into a goldfish would still be Wikipedia’s version of truth.
Is that it? No attempt appears to have been made to vandalise a page that contains information that actually matters to anyone in the modern world, that is, information that would affect their livelihood, income, or health.
So, while I agree that misinformation can persist, it is still unproven that important misinformation will persist for very long.
And as for your point about finding a more reputable source; that is surely one of the things that Wikipedia helps you to do.