The problem is it is harmful to others. There is always someone who is willing to work for less or worse conditions which collectively affects everyone.
Really? It appears that's not the case, and "competition" means those with leverage (both with capital and technology) are able to capture an ever increasing amount of wealth compared to the rest of the working class.
Funny how "competition" is great as long as you're on the "winning" side.
I think you're misunderstanding what I'm saying. I apologize for poor phrasing in the previous comment. Let me see if I can more clearly explain with an example.
Imagine the question is, "Is purchasing food with money perfectly fine?".
Most people would agree that trading money for food is fine so long as it's consensual and both parties agree (i.e. assuming there is no coercion).
If one party used violence, or threats of violence, to get the other party to make the trade, that would be coercion. Most people would agree that this type of "trade" is not okay.