Matthew 9: The pharisees accuse Jesus of blasphemy

According to the merian webster dictionary, blasphemy is:

1a
: the act of insulting or showing contempt or lack of reverence for God accused of blasphemy

b
: the act of claiming the attributes of a deity for a mere man to suggest that he was … divine could only be viewed … as blasphemy—John Bright †1889

We read:

1-3 Back in the boat, Jesus and the disciples recrossed the sea to Jesus’ hometown. They were hardly out of the boat when some men carried a paraplegic on a stretcher and set him down in front of them. Jesus, impressed by their bold belief, said to the paraplegic, “Cheer up, son. I forgive your sins.” Some religion scholars whispered, “Why, that’s blasphemy!”

A mere man can't forgive sins in general of anyone. He can forgive only sins addressed to him. In this passage, a paraplegic man's sins are forgiven by Jesus. No wonder the pharisees accused Jesus of blasphemy because they couldn't see Jesus as the son of God. Jesus answered showing a sign that he was no mere man: he cured the paraplegic man.
It raised a question to the pharisees: is Jesus with divine authority as he makes signs that no mere man can do? Jesus made many more miracles and signs but it interesting:

32-33 Right after that, as the blind men were leaving, a man who had been struck speechless by an evil spirit was brought to Jesus. As soon as Jesus threw the evil tormenting spirit out, the man talked away just as if he’d been talking all his life. The people were up on their feet applauding: “There’s never been anything like this in Israel!”
34 The Pharisees were left sputtering, “Smoke and mirrors. It’s nothing but smoke and mirrors. He’s probably made a pact with the Devil.”

Here, the pharisees created an explanation. Jesus made a pact with the Devil and so he could perform such miracles. The pharisees attributed signs made by the Holy Spirit to the devil, and so (as in Mark), the pharisees blasphemed against the Holy Spirit.
King David was a Messiah, anointed by the Holy Spirit, however, he didn't perform any miracle. The gospel of Matthew presents Jesus in a far superior way than David. He makes the reader answer: Was Jesus the Messiah? Do you submit to him? Depending on the reader's position he is a citizen of God's kingdom or not.