I don’t trust my sister’s boyfriend

My sister recently began dating a guy who says he loves her a lot but also has some strange posts on Facebook. I always check on who she is dating because I am protective of her, so I showed her the posts and asked her to be careful. She laughed it off saying he is a little strange but also kind and considerate. It has been four months since they got into a relationship and, whenever I meet him, I am always more certain that he is not who he pretends to be. I want to get her to break up with him, but she won’t even take me seriously because she just thinks I am being her over-protective older brother. What should I do?
You can continue to be her protective older brother by making sure she knows you are looking out for her and allowing her the freedom to make decisions that concern her life. She will inevitably make mistakes as she gets older, and part of learning what is right and wrong, or who is right and wrong, involves making those mistakes and learning from them. You have done your part by telling her what bothers you. What she does next is up to her. Also, keep in mind that the only people really qualified to gauge a partner are the two people in that relationship.

Should I tell my boyfriend that I want to end this relationship because I don’t support his political views? Am I being too shallow? I just don’t accept anything about the parties he supports.
If his views offend you, there is nothing wrong with using that as a reason for not wanting to be with him. Political views affect all aspects of our lives, whether we choose to accept this or not. If you don’t see things from his perspective, or vice versa, you are entitled to be with someone who has the same points of view as you do.