T isn't atheists or barbarians who receive the biting words of judgment meted out in this chapter. It's the religious crowd. The scribes and the Pharisees were locally famous for their extreme piety. Yet, the only words Christ had for them were words of rebuke.
The Pharisees talked big & walked small (vs. 3). They required much but contributed little (vs. 4). Their devotion was not to God, it was to themselves (vs. 5-7). They wanted to lead, but they did want to serve (vs. 8-11). These men were lost. They were on their way to hell (vs. 14-15). They had long lists of rules to follow, but everything was superficial. Jesus described them as dead, unclean, hypocritical & iniquitous (vs. 27-28). He called them snakes & murders (vs. 33-34). They were religious, but lost.
In our modern world, there are so many different religions. But there is only one true and pure religion. Only devotees who have received Christ are acceptable. The rest of the world's religious people are following nothing less than the inventions of Satan himself. The occult, cults, dead Christianity & all contrived religions offer no legitimate hope.