Although Jesus was speaking the truth because he is the Truth, those people did not have the revelation from heaven to be able to see and understand that truth by the help of the Holy Spirit.
They had a doctrine and religion and a lot of legalism but not a heavenly revelation about what Jesus was saying and doing. Today we should be careful that we do not dismiss a spiritual experience of other Christians as not valid, just because it does not fit our doctrine.
They may have a revelation from the Holy Spirit which we do not have. And the only way to understand correctly the Word of God, is by revelation from the Holy Spirit because the Word of God is from him. The rest is about theology, doctrinal interpretation, legalism and philosophy. Yes Theology has its own importance and place in the body of Christ, but there is also a revelation from the Holy Spirit for the body of Christ too.
Let Us Study the Bible 