Hey Tangi I work in a job where listening(in this case reading) is as important as speaking(in this case writing).
You ask, "Why is that such a bad thing to do?"(trading). There is nothing wrong with trading. I did very well trading trusts until the Government hit me big time with their taxation rule change. What I object to, is posting in a fashion to go along with where you/me the trader wants the price to go to at that time. This, the sky is blue, than the sky is falling mentality can be harmful to the less informed investors who don't understand that the trader is not an investor(long term).
This is what I posted and you appear to have not listened to(read), "This type of talk though can cause a less experienced investor to sell prematurely. Although the traders intent may not be to take advantage of any individual necessarily, it does."