There is nothing wrong with praising God. It is encouraged and commanded thousands of times in the bible. The reason the Pharisees were so upset was because they didn't accept Jesus as God. It would be blasphemy for Jesus to accept worship if He wasn't God. This is another confirmation of the deity of Christ.

Only Luke in 19:29-40 records this instance of the Pharisees' objection and Jesus' answer. This was the triumphant entry of Israel's King that was prophesied and anticipated for centuries. The excitement could not be contained. If people refused to praise Him, the creation would have broken out in praise. No rock should have to do what God created us to do.

By compiling all of the writers' accounts of what the multitudes were saying, we have this record: "Hosanna to the Son of David" (Matthew only). "Blessed is he" ("the King"--Luke "the King of Israel"--John.) "that cometh in the name of the Lord. Blessed be the kingdom of our father David that cometh in the name of the Lord" (Mark. only). "Hosanna in the highest" (Matthew and Mark only). "Peace in heaven, and glory in the highest" (Luke only).

Pride was what caused satan's original sin according to Isaiah 14:12-14. He wanted to be like the most High. One thing reserved for God alone is worship, and the devil has always sought that. If he can't be the one to receive worship, then he seeks to turn others away from giving true worship to the most High God. This is the reason why praise and worship to the Lord are such powerful tools against Satan. He can't stand to see God worshiped.