SERIOUS QUESTION why are republicans so against gay marriage and abortion?

Your question is harder than you think because there isn't just ONE reason. There are many reasons. This is because people are Republican for different reasons.

Some people are Republican because they feel that party reflects their religious views. Those people may be against gay marriage and abortion because they feel their religion is against it.

Some people are Republican because they feel that party reflects their fiscal views. They are not necessarily against gay marriage and abortion, at all. In fact, there are even gay Republicans.

Some people are Republican because they feel that party reflects their views about protecting the family. They think that family is the building block of society. Anything they view as weakening family (which, they may feel, must be made up of a wife, husband, and children), they are against.

Of course, a case could be made that allowing abortion strengthens marriage because then people do not have children they don't want outside of marriage. Likewise, a case could be made that allowing gay marriage strengthens marriage because then there are more marriages and more children growing up with married parents (which, in turn, means they are more likely to become married and stay married themselves).

Ultimately, there are many different reasons my many Republicans are against gay marriage and abortion. No one answer fits all Republicans.