Meeting the parents is always a nerve-wracking thing because first impression is usually the biggest impression for most of us and when you realize that there is an unusual vibe, you can't help but to hear a pin drop. You could just be sitting there spreading humor with the family or just casually talking and then next thing you know, you are sweating bullets like "What is going on here!" and then your partner feels embarrassed not knowing how to change the mood.
So what do/would you do if the parents don't like you?
For some people they just let it be. They see the situation as they are only in the relationship with their relative not the family members themselves. They can't help who they are nor can the family help how they feel. Others feel bad and will discuss with their partner about the status of the relationship because they are part of the family especially if they choose to get married or have kids. This is something that should definitely be talked about because it test the communication of everyone as well as the level of love involved the family and the couple itself. The best thing that anyone can do is to respect each other despite if they hate each other or not.
Here is a clip on "The Real" perspective on how to deal with the parents not liking your partner: