Informing the author about a mistake is usually OK. But the "I had to stop reading here" line sounds dismissive and somewhat rude. But I may also be wrong abou

Informing the author about a mistake is usually OK. But the "I had to stop reading here" line sounds dismissive and somewhat rude. But I may also be wrong about why people downvoted you; sometimes it just seem random, so you shouldn't take it too seriously.