If your gynemostia is idiopathic would taking tamoxifen or raloxifene be harmful?

Unlikely: These are both very safe drugs to use. Yet I am not aware of any experience in using them for gynecomastia and whether they can help or not. You could try under the supervision of your doctor if he/she is open to this idea.

Most prefer surgery: Whatever your age, most men with gynecomastia prefer surgery, which is effective, definitive and easy. I'll trust this is not pseudogynecomastia and that your thyroid and liver are in good working order. Tamoxifen is acceptable if for some reason surgery isn't right foryou.