According to utilitarianism, it does not matter how many people suffer a negative

Utilitarianism is the "greatest good for the greatest amount of people." So... According to utilitarianism, it does not matter how many people suffer a negative as long as more experience a positive.

We tend to align our beliefs and values with others of like mind. Think of your friends. If you had huge differences in personal beliefs and values, they probably would not be close friends. You would not be as comfortable with them. You could not truly support them and vice versa. With politics, if you do not believe in abortion (for example), and believe that is a baby being killed, you could not truly support, and align with, a politician who believed in abortion. We try to find politicians qualified for the job, but that we feel is truly aligned with our personal beliefs and values.

Hope this helps! :)