The Short Version
This claim is false. It conflates overall internet traffic — where bots may account for ~51% — with content engagement on social media platforms, which is a fundamentally different metric. The best direct evidence, a peer-reviewed study, finds only about 20% of social media activity is bot-generated. Even the highest platform-specific figure cited (40% of Facebook posts being machine-generated) measures posting volume, not engagement, and still falls short of 50%. No credible source supports the claim that bots generate more than half of social media engagement.