It depends on what one is referring to. My church partners with other local churches and jewish synangogues to provide volunteers for a local foodbank, and the local chapter of Habitat for Humanity. I can't imagine why Christian would have an issue with this, but some, no doubt, do.
Yet Jesus says "whatever you to do the least...". It's a misonomer to think that proclaiming the Gospel is limited to one's lips moving. Most often, it's more effectively done by having one's hands and feet moving. I'm of the opinion that a hungry man can't be spiritually fed until he is physicall fed first.
We do that too and can't understand why others would have a problem with that. In fact, our denomination is the longest supporter of Habitat in our metro area.
On a related matter, on Sunday nights, we provide sandwiches to the homeless downtown and then have a time of worship and prayer. Sometimes, it's not an issue of one versus the other, but actually doing both -- acts of mercy plus verbally sharing the Gospel.
But I don't think we always have to share our faith verbally. I'll never forget a most wonderful compliment some time ago from someone I was helping. They said, "some people talk about their faith, you actually live it." It reminded of the song "They'll Know We Are Christians By Our Love."