I am not 100% sold on this notion that Christians should not permit themselves to be influenced by secular culture.
"Christians who permit themselves to be shaped by secular culture are guilty, not only of betraying God, but of losing their own true selves." - W. Paul Jones
Mostly, because whether we like it or not, we are surrounded by secular culture from the moment of our birth. It is a lens that influences how we interpret the world around us and our role in that world. It's how we begin to understand how things work, it's how we pick up on social cues, and it's how we learn to speak to one another.
In essence, our interaction with secular culture determines how we live.
It is impossible not to be shaped by secular culture.
Moreover, I'm not sure that I think we should try to avoid it.
If we aren't shaped by secular culture, then we lose the ability to truly proclaim the Gospel.
For example, we see in our very own pews and congregations people who do not understand words that people in seminary think are obvious - words like discernment, sanctification, or ecclesiology. They just do not have a place in the vocabulary of most people.
By failing to be shaped by the secular culture - such as the language, the tools, the knowledge - that come up out of the larger culture, we make ourselves even less understandable to the very people who want/need to hear our revolutionary message.
I think social media is a great example of how we are shaped by secular culture, but it allows us to serve God and claim our Christianity.
In our 140 character tweets, we are able to focus our message down. By doing so, we force ourselves to really engage with the thought/idea and make it a part of ourselves. We then are able to use a language that we have grown up in to then speak that idea to others.
We become translators of the Gospel.
I'm not suggesting we fall prey to the secular culture that worships sexuality, drugs, and violence, but we do need to be aware of their existence and their prevalence.
Christianity cannot work in isolation from the larger world.
It's only by engaging the larger world that we are able to see where our own flaws and failings reside.
For example, Darwin and his theories of evolution forced us as Christians to re-think how we read scripture.
Do we read the scriptures literally or metaphorically?
The result of that conversation has helped bring us to a new understanding of how we can read scripture today.
When we insulate ourselves from secular culture, we cut ourselves off from new opportunities to learn and grow.