Adulterers and adulteresses are people who have extra-marital affairs. From the perspective of the operational mechanism of human mind and psychology, they are considered to have a condition of psychological disorder : relationship addiction. They get immersed into the object of infidelity out of compulsion caused by stress and they cannot stand being exposed to stress and wounds responding irrationally. 

They will express extreme resistance against anything that hinders or objects their ideas or behaviors regarding relationship addiction. On the other hand, they will express extreme liking toward anything that promotes or supports their relationship addiction. 

 https://youtu.be/3g-uNpS52eY

When you develop relationship addiction, you may develop positive emotions toward a wrong person, which may also change your thoughts and behaviors. Then, you may fall for distorted human relationships and destroy normal and happy relationships. Some people may argue that they just had some fun and it is nothing serious. Then, why would they try to hide the fact of infidelity, which is just for a little fun? They try to hide the fact of infidelity since they have developed emotions toward the object of infidelity, which they themselves have taken quite seriously. People with relationship addiction have developed distorted habits of perception and expression, so they think and behave in the opposite ways from people with normal psychology. They like what normal people dislike and dislike what normal people like.