Tags do not boost your SEO at all, they rather help your video appear in the Recommended Videos section on the right of a YT video.
When I tagged competitors I was simply telling YT that it can show the videos to people watching another video from one of KalariLab's competitors.
There are 3 main ways to get views on YT when your channel is small:
1. SEO; 2. Homepage recommendations; 3. Recommended videos on other video pages.
The tactic with tags works only for the 3rd category above.
I hope that settles this discussion once and for all.
Sidenote: I still don't understand why this post was flagged...
People watching your customers' competitors are not yours to target through their brands, but you can target them through keywords that describe the content, not to use the names of your competitors.
The fact that you are still arguing this is proof positive to me that you are an unethical operator and that this is not just an innocent mistake.
This post was flagged because it is low value, unethical and ultimately an attempt to do to HN what you are already doing to youtube. You will find that HN has considerably more effective anti-bodies against SEO 'specialists' (I use the term liberally) hijacking the audience than youtube has.