There is the statement, "You can tell the truth without loving but you can never love without telling the truth." Lost people tend to say, "You are not being loving with telling us our religion is wrong." The opposite is quite true that when I tell them that they are lost, it's because the Lord Jesus Christ loves the sinner too much to sugarcoat the truth of the Gospel, that they are lost and headed to Hell. Today's "love gospel" is one gospel which is not another and it is not real love. It's very often to see people accuse the true Christians of just looking for fights whenever they attack other people's religion while they would see the "beauty of Christianity" in nominal Christians who accept other people's religions. One of them even praised the late Pope John Paul II for ecumenical dialogues or the incumbent Pope Francis for continuing the same ecumenical dialogue.
1 Corinthians 13:6 says that love does not rejoice in iniquity but rejoices in the truth. If you love the person, you tell them the truth out of concern for their well-being. If you love people, you don't want to withhold the truth just because they will be upset or angry. A parent who loves his or her child gives just punishment for the child as Proverbs 13:24 says that whoever spares the rod hates the child but whoever loves their child punishes them when needed. The same goes for why Christians tell people their religion is false and that they are on their way to Hell. If I told any Roman Catholic that Mary can't intercede for him or her and that he or she should go directly to Jesus for salvation, it's because I care for that lost soul and not because I want to stir up a fight.
The reason why Jesus would not accept other people's religions as true is because they based on Satan's deception leading multitudes into Hell. Remember when mankind fell, anything mattered to them but God and they would care less about offending God as long as they are accepted by men. That is the total depravity of man at work where they need to be saved in order to be regenerated into a new life. People are foolish when they worship the work of their hands because their gods could not save (Isaiah 2:8). People are foolish to think that their own personal righteousness will get them straight to Heaven (Isaiah 64:6). God sent first prophets, second apostles and later preachers after both the age of the prophets and apostles ended to warn people to repent of their evil ways, seek God and live. He sent Jesus Christ His only begotten Son but what did the world do? Most of the people just rejected those whom God sent and I am not surprised considering Jesus warned in John 15:18-19 that they hated Him before they hated His followers.
If there's any proof of real love that is so visible is when the Christian chooses to endure suffering to the point of death rather than compromise the truth. When Christians choose to endure to the end, it's the grace of God at work in their lives. Apart from that, they have no ability to endure to the end but because God is with them, they possess it. When Christians chose to be die instead of renounce their faith, it was also because they love the multitudes they were preaching the truth to. They did not want to compromise the Gospel with the world that's why they chose to die. While it seems foolish to the human senses but it's that kind of love that caused Christianity to grow in the midst of persecution. They endured persecution because they love people enough to warn them that they are lost.