The message on the sign in the header image is a Biblical one. If you know only one of Jesus' teachings, it is probably "love your neighbour as you love yourself". I would even go as far as to say that if you don't know this basic teaching, you are not a Christian, and I believe there is fairly strong Biblical precedent for this (1 Corinthians 13:1-3; 1 John 3:10-15; 1 John 4:7-11).
Yet, a surprising number of professing Christians often object to the message on this sign. Whether it shows up on a sign, a t-shirt, a meme, or any other media, you are all but guaranteed to find a host of bigots screaming about how Christianity is the only true religion, and about how things like homosexuality are sin. Apparently, the radical Left are not the only ones who need to be taught that love and approval are not synonymous! Love takes no pleasure in iniquity, but rejoices with the truth (1 Corinthians 13:6). So do we have to love homosexuality, or Islam, or various other sins and false worldviews in order to love the people who commit those sins, or believe those lies? No!
The Biblical teaching is to love your neighbour, and even your enemies. My brethren, even if someone is actively persecuting you, you have no right to hate them. Jesus' command is to pray for them (Matthew 5:44-45). This sign should not be as controversial as it is. If we claim to be Christians, the only legitimate response to it should be "amen". Save the mindless hatred for the children of the devil.