Abnormal = not normal = deviant. Those all mean the same thing. There is nothing improper about not being normal, being abnormal or being a deviant from the norm. If your morality is built on conformist notions then that might be hard to accept, but a lot of things that were considered "normal" are now recognized as being immoral behaviors.
Abnormal does not mean ignorant, unitelligent or deformed. Abnormal is an adjective that often describes another adjective. Alone, it just means not normal. A sentence that reads...
Jack was abnormal.
Leaves the reader wondering/asking in what way. He could be abnormal in a way that is good, bad or indifferent. But all we know is that he is not normal. He could be abnormally tall. Some might see that as a positive, negative or, like me, indifferently.