I think it really depends on your goals as a writer. If you're wanting to use your talents as a writer to bring people closer to God, then your audience should be people that will read that. The thing about christian writing, and I'm using christianity as a basis because it's my personal belief and CTD's, is that the core audience are already christians. For instance, take the Left Behind series. Sold primarily in christian book stores, to people who have already accepted Christ. The author probably had the intention of telling a story of the rapture to non-believers, but ended up selling to the already-christian audience. I'm not saying that the series doesn't reach other groups of people, but that's not the primary focus. It generally helps bring christians closer to God while helping foster a better working relationship with Jesus Christ.
On a broader approach, your core audience isn't quite the same when you're writing to glorify the Lord. From a christian and religious standpoint, yes, you will be criticized by christian groups for pandering to the secular audience, but you need to come to terms with the type of writing you want to put out. If you are being called to write to a christian audience, by all means, you really should follow what that audience wants, and not stray. By straying, you alienate your core audience, therefore destroying their "faith" in you as the author, and their belief that you are indeed trying to minister to them on a christian level.
On the other hand, if you are writing "for money" or you're looking to expand your reign of influence, then you must write to what the audience expects. I don't believe that's compromising your beliefs, and I don't think it's going to hurt anything in the long run. If, due to your beliefs, you feel it's not the kind of writing style you should be doing, by all means, don't do it. One should only write to where he feels comfortable.
You shouldn't have to compromise anything. There are ways to reach the secular audience, and still glorify Christ {or hold to your beliefs, whatever they may be}. But to reach your core audience, you should really write to their level. If you are writing to what you believe, then you have already changed your audience to those people that believe the same thing. People like to read authors that help foster their own feelings/beliefs.
It's all in what you want to write, and who you want to write to, not in what you believe is right.