I do not accept human praise/testimony. Where do we get the strength to continue doing good when we find ourselves facing opposition and persecution? Where does our will power come from? Jesus’ life and ministry was all about doing good to his brothers and sisters. He was healing the sick, feeding the hungry, and raising those who were bowed down with the burdens of life (the poor and the disenfranchised). It was a mission for which he would end up giving his life. Jesus was well aware of where his love for his brothers and sisters would take him, perhaps the reason why he didn’t back down in the face of harassment and persecution. 
Following the healing of a crippled man by the pool at Bethesda (cf. John 5:1ff), those who were opposed to him immediately went to work. They not only harassed the man who had been healed, but they also attempted to intimidate Jesus. However, Jesus was not ready to be cowed. He stood his ground and took the opportunity to remind them that he needed neither their approval nor human praise/testimony to back him up. What he was doing already had the backing of his Father (yesterday’s Gospel Reading). 
Jesus refused to bow to the request of the Jews on two grounds: Firstly, he was aware that human testimony would be short lived because of the people’s lack of faith (or shallow faith). John testified to Jesus’ authenticity and even though for a little while the people rejoiced, it did not last long. Even Moses and the other prophets foretold of his coming (cf. Deuteronomy 18:15: God will raise a prophet like me; you will listen to him…), yet they were still refusing to believe in, and listen to him. Even if others were now to testify on his behalf, it would serve no good. Secondly, Jesus told the people that if his actions and words were about the truth, then that truth will become self-evident. He didn’t need to be backed by what the people had to say. He was going to let his actions speak for themselves and on his behalf. When pagans and non-believers will come to believe in Israel’s God, then those who were doubting his authenticity will clearly come to see that Jesus is truly from the Father and that he is doing God’s will. It is in the knowledge that he is doing God’s will that Jesus will rely. His life and ministry was to be his testimony.