"Truly I tell you, among those born of women no one has arisen greater than John the Baptist; yet the least in the kingdom of heaven is greater than he. From the days of John the Baptist until now the kingdom of heaven has suffered violence, and the violent take it by force" (Matthew 11:11-12 NRSV).
John the Baptist, whose life and ministry was closely interwoven with that of Jesus, has been arrested by Herod Antipas. In prison he has heard of the ministry of Jesus and sends emissaries to ask if, in fact, Jesus is the Messiah. Jesus reply is simple: "Go and tell John what you hear and see" (Matthew 11:4). Jesus does not need to claim a title; the words and demonstrations speak for themselves.
Jesus then comments on the relationship between his message and that of John. John is like the last of the Hebrew prophets; among those working upward through mortal consciousness to spiritual awareness, no one has risen further. But the new consciousness Jesus teaches—the kingdom of heaven consciousness—is something entirely different. It's already present within. We don't struggle to achieve it; we simply surrender to it. And when we do, we will find that our understanding is effortlessly greater and more expansive than the fruits of religious struggle.
It's in this context, I think, that the word you question—“violence”—can be best understood. People—including John the Baptist—have felt it necessary to achieve spiritual consciousness by struggling violently to overcome the distractions and delusions of the mortal world. We often still have that attitude today—that we must struggle, fight and resist violently in order to stay centered on our spiritual path. But struggling and fighting presupposes a resistance—a force seeking to hold us back—and that supposition then becomes reality if we believe in it. The path of Jesus is not one of struggle, but one of surrender to the kingdom consciousness that already lives within us.