Fr. Haydock interprets our Savior's words to mean penances, mortifications and doing violence to the flesh, not to others. "Suffereth violence It is not to be obtained but by main force, by using violence upon ourselves, by mortification and penance, and resisting our perverse inclinations. (Challoner) Certainly it is great violence for a man to look for a seat in heaven, and to obtain that by his virtue which was refused him by his nature. (St. Jerome in St. Thomas Aquinas) The kingdom of heaven That is, the kingdom of heaven is to be obtained by mortification, penance, poverty, and those practices of austerity which John, both by word and example, pointed out. According to this interpretation, the kingdom of heaven means eternal life. Or the meaning may be, the kingdom of heaven is taken by the violent, because it is not now confined, as in the old law, to one people, but open to all, that whoever will may enter in and take possession of it. The kingdom of heaven, in this interpretation, is taken for the Church of Christ, for the gospel, and also for eternal life. (Menochius)" https://catenabible.com/com/5735e2b1ec4bd7c9723bf729
Our Savior said those who live by the sword will die by the sword. We see both Hamas and Israel - Christless people - live and die with swords/guns rather than strive to live in peace. St. Paul counsels us, "If it be possible, as much as is in you, have peace with all men." (Rom 12:18) So the exhortation to "violence" in the Gospel must be interpreted as Fr. Haydock interprets it above, namely to do violence on one's passions, on one's sins, and one's evil desires, on the devil, the world and the flesh. Then one will have true peace within and without.