We should remember that God made every human on this earth. He loves every person of every religion because they are all his children. No one person is closer to God than another. We may call God by different names, but they all mean "Father". Only when we die, we will know the truth.
I believe that every religion teaches something positive, that you cannot deny is right. They each hold truth and have similarties.
The combination of two religions will bring something more positive.
Remember before the Gurus, before Mohammed, there was God. That one constant in every religion.
It's not wrong to marry someone of another religion, you will be marrying another person that God loves.
I don't see why a Sikh should stop practicing sikhism once he marries a Catholic. Or vice versa. Their children can be brought up respecting both religions. It can work.
I believe everyone has a valid point. It is far easier to marry someone of the same religion. But easier doesn't mean better. Once you fall in love all of it is easier said than done.