Slamming other companies or the word I use is “slagging” is just not acceptable or professional in my opinion.
If you want a good reputation online then slagging other companies to promote your own is the not the way to go.
It can damage your online reputation and online presence and is unethical. In the “real” world, it could be seen as slanderous.
In the long term it will do you no good at all. Anyway, I feel strongly about this so I did a video to express my views about it in the hope it stops people doing it.
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