So you filter all requests for advice and decide not to answer them if you think the answer is obvious (clearly not to the user or they wouldn't ask) - well thats up to you. So why post a sarcastic reply?
Psychologists determine that those with a personality that seems perpetually cynical and hostile such as people who are constantly putting others down, criticizing everything, and making cynical comments have low self esteem and a desire to raise oneself by publicly lowering others. They haven't learned how to constructively express their anger. Not surprisingly, they aren't likely to have many successful relationships. This anger is usually based on frustration. This frustration may be due to self perceived lack of achievement such as in their education or job, or sexual, financial or other difficulties such as an unhappy relationship with a partner, parents or other family members.