The Pharisees were very embarassed by the man's
healing and by the reaction of the crowd. They had
decided that Jesus was an imposter so they had to
find some way to explain away the miracle. They
couldn't deny it without looking ridiculous.

Notice too that when miracles are rejected, people's
hearts get hardened, like Pharoah's. Even today
when the power of the supernatural is rejected there
can be the same results.