Spamming in any form is super risky mate, especially on platforms like Youtube. While it might be tempting to extract replies from a competitor’s live stream and spam those users, you're just asking for trouble. Youtube has strong anti-spam and anti-abuse measures, and you could easily get your account flagged or banned.
Instead of spamming, why not use the live chat as a goldmine for targeting? You can see who’s engaging and figure out who might be interested in your stuff. Tools like https://socialblade.com/ or https://vidiq.com/ could help you track your competitor’s performance and audience. Also, if you want to get those users’ attention, focus on creating valuable, organic engagement, reply to comments, start meaningful conversations, and build your community the right way.
Trust me, the long-term benefits are way better than trying to game the system.