Being less pessimistic about dating requires that you avoid judging new dating prospects based on negative experiences that you have had in dating in the past.
It can be difficult to do this because as human beings, we tend to use our past experiences to prejudge people.
The men who become paranoid or bitter about dating women after dating a horrible woman may have given a lot of themselves to those relationships.
These were women that they may have put a lot of their trust in. That trust was betrayed in some fashion by the horrible woman and the men become paranoid and bitter.
People respond to a sense of betrayal in different ways.
Even if he were to acquiesce because he cares about you so much and is more concerned about losing you than anything else, there will come a time when he will most likely detest you.