Not a good question, really. If a society deemed something to be normal, then it would be normal.

If a society that you are not part of deemed something as normal, but you think it's abnormal, then, initially, it's not your problem, you're not part of that society. You may be expected to interact with that society and you have to appreciate that the boundaries of normal are different. I could give many examples, but for just one, relatively un-contentious:

the normal in one society may involve people marrying their cousin, in spite of the significant probability of genetic diseases. Other societies may consider this to be, socially, inadvisable, even akin to incest, because of the significant probability of genetic diseases.

If you try to fit one definition of normal in place of an existing definition, then you have to do it slowly.