If you understand what a Catholic believes and why he believes it, you will know why he is “intolerant”.
Case 1: Baptism. To a Catholic, baptism is freedom from original sin and inclusion in the Body of Christ. Baptism is a requirement for attaining salvation (John 3:5). If you seek to deny her child baptism, it may be seen as you denying his spiritual welfare and trying to damn him.
Case 2: Homosexual acts. Clearly condemned in the Bible in both the Old Testament and the new, homosexual acts are intrinsically disordered and mortally sinful. To a Catholic, they are both a vile offense before God and a pathway to hell. We are “intolerant” because we realize this.
Jesus preached compassion, not tolerance. Sinners should be welcomed and loved (compassion) but not left to continue in sin (tolerance). Tolerance is evil’s refuge from truth. Tolerance is a lack of compassion for the sinner.