Here is an example of a metastudy of spanking. Its conclusions are not entirely black-and-white and it finds that a large number of the studies done were flawed--not because they were politically motivated, as you assume, but probably because they were simply poorly conceived--but it still finds persuasive evidence of correlation between spanking and negative behavior.

Don't be too hasty in dismissing self esteem or in assuming that you know what someone else understands when they speak of it.

https://www.scientificamerican.com/a...bout-spanking/