No the 'general rule' is that in certain situations you do something not to appear to be disrespectful in some way. So for example if you were to work at Ycombinator the 'general rule' would be to try and encourage others to use yc instead of someone who competes with YC. Ditto if you work for a department store it would be typical to be supportive in some way for your employer (who gives you a job) and not if you can afford to shop at one of their competitors. For some reason this has been lost in the new economy.