As far as I know, Muhammad had been preaching Islam in a way very hostile to the Meccans.
Al-Tabari:
Ibn Humayd- Salamah- Muhammad b. Ishaq- Yahya b. ‘Urwah b. al-Zubayr- his father ‘Urwah-‘Abdallah b. ‘Amr b. al-‘As: I said to him, "What was the worst attack you saw by Quraysh upon the Messenger of God when they openly showed their enmity to him?" He replied, "I was with them when their nobles assembled one day in the Hijr and discussed the Messenger of God. They said, ‘We have never seen the like of what we have endured from this man. He has derided our traditional values, abused our forefathers, reviled our religion, caused division among us, and insulted our gods. We have endured a great deal from him,’ or words to that effect. While they were saying this, the Messenger of God suddenly appeared and walked up and kissed the Black Stone. Then he passed by them while performing the circumambulation, and as he did so they made some slanderous remarks about him. I could see from the Messenger of God’s face that he had heard them, but he went on. When he passed the second time they made similar remarks, and I could see from his face that he had heard them, but again he went on. Then he passed them the third time, and they made similar remarks; but this time he stopped and said, ‘Hear, men of Quraysh. By Him in whose hand Muhammad’s soul rests, I have brought you slaughter.’ They were gripped by what he said, and it was as though every man of them had a bird perched on his head; even those of them who had been urging the severest measures against him previously spoke in conciliatory ways to him, using the politest expressions they could think of, and said, ‘Depart in true guidance, Abu al-Qasim; by God you were never ignorant.’
So the Meccans left him alone until they could no longer tolerate his derision of their way of life; a way of life which had not hurt Muhammad in any way. The Meccans had warned Muhammad over again that if he did not stop his derisive remarks, they would put a stop to him, so to speak. Muhammad continued reviling them and their gods; he slaughtered poets who mocked him in verse (Asma Bint Marwan, in Ibn Ishaq's Sirah Rasul Allah) and more.
And also Muhammad apparetly threatened to slaughter them a la the above hadith, so...