You haven't mentioned the complete sentence => "98% of Indian Population have not even heard the word "Github" in their entire life, yet everyone acts like they know this stuff".
The problem is "They try to act" like they know about software industry, meanwhile when you try to explain them that you are working on some open source project, they refuse to respect your opinion.
Read the previous paragraph in the article. The point was that "everyone" assumed they understood how well he was doing, while being unable to evaluate that. (E.g. never heard of github.)
The problem is "They try to act" like they know about software industry, meanwhile when you try to explain them that you are working on some open source project, they refuse to respect your opinion.