Now obviously unspotted in this verse is talking about keeping oneself clean of worldly infection.   

However, I want to focus on the alternate meaning of unspotted - 'not seen'.   

Christianity is largely unspotted in the Seven Mountains of influence.   

Actually it is unspotted from day to day life as most Christians live just like non-Christians.   

We are to be the light of the world.   

You are the light of the world.     A city that is set on an hill cannot be hid. - Mat 5:14 Jesus is the llght and by receiving Him through the New Birth by the Holy Spirit we become light.      We ought to recognize the responsibility upon us to let our light shine.

Neither do men light a candle, and put it under a bushel, but on a candlestick; and it gives light unto all that are in the house. - Mat 5:15 freely we have received, freely we should give.     This happens as we make opportunity for the light that is in us to be manifested wherever we go.

I think it is safe to say that Jesus expects us to be 'spotted' by the world just as James is saying we should be unspotted from the world.   

Niceness and 'good deeds' can be pulled off by non-Christians as well as by Christians.   

So, niceness and good deeds are not how we let our light shine.   

How then do we do it?   

We are commanded to preach the Gospel to every creature.   Mar 16:15

We are commanded to be witnesses.   Act 1:8

We are commanded to heal the sick and set the captive free.   Mat 10:8

I am quite sure that if our lives had a significant amount of preaching, witnessing, healing and delivering going on we would be spotted by the world.   

I am also quite sure that this would make us salt and light.   Mat 5:13 Mat 5:14