Is killing animals for food a good idea?

I have eaten non-vegetarian food in the past and still eat egg regularly. And I don't regret having eaten animals in the past. So I am definitely not a fanatic vegetarian! Then why did I stop eating non-vegetarian food? Because somewhere deep within I feel killing animals for food is not right. But then a lot of religious Hindus also eat non-vegetarian food. Even some of the most respected Hindu saints like Vivekananda and Ramakrishna also used to eat non-vegetarian food (mainly fish). So then what's wrong with eating non-vegetarian food?