Koran 25:63. And the servants of Most Gracious are those who walk on the earth in humility,
and when the ignorant address them, they say, Peace!'
Koran 28:55. And when they hear vain talk, they turn away therefrom and say,
'To us our deeds, and to you yours, peace be to you, we seek not the ignorant'.
Koran 19:47. Abraham said (To his mushrik father), 'Peace be on thee, I will pray to my Lord for thy forgiveness, for He is to me Most Gracious'.
Koran 43:89. But turn away from them, and say 'Peace!' But soon shall they know!
Allah says in the above verses, that you can give Salaam to the Kufaar. Its true that its narrated in Saheeh Muslim, not to give Salaam first. That was said because you don't know how they will respond to you. If they say, 'Asalamu Alaikom' you can say, 'Walaikom' according to the prophet. You can even say 'Walaikom Salaam Warahmatullah' according to Ibn Qayum and other scholars. But the prophet said that we have to say, 'Walaikom' because sometimes they said, 'Asamu Alaikom' which means, 'Death be upon you' so the prophet said that we have to say, 'Walaikom (And upon you)'. Other scholars said that if you do Dawa, you can greet them with Salaam Alaikom. How do you want them to become muslim, if you don't wish them peace? So Insha'Allah, you understand what i mean.
Allah knows best
:w: