To look at this topic, I feel you first have to find your definition of good and bad. Let us define good as that which does not hurt anyone or remove his or her freewill and bad as that which goes against a person’s nature or causes injury of any sort. I do have to say that I prefer not to even contemplate the kind of magic that is done with the specific purpose of hurting or even killing someone.
If you ask is there such as thing as bad magic and use the definition above, then yes there is bad magic and it abounds. Performing a love spell with someone specific in mind takes away freewill and I do not feel is the type of magic that should be done. Anyone in his or her right mind would eventually start to wonder if the object of their affection really loved THEM or if it was a product of the spell.
The spells that someone may perform in anger usually turn out to be bad. Magic should be done with pure intentions and when a witch is angry, the mind thinks of all kinds of forms of retribution, most of which should not see the light of day.
I follow the Rede and always think of the consequences of what I send out..is it something I want to return to me three times as strong? If not, then I file it under bad magic and leave it alone.