I am a theistic evolutionist.
My two greatest struggles in faith are loving creationists, and not damaging the faith of creationists.
You know, I've been focusing on your first struggle; I thought it was time to say something about the second.
if you're talking about their faith in Christ, then I would respectively suggest that there's no way you could damage that.
If you're talking about faith in something else -- maybe something they hold in the same regard or have associated with Christ that perhaps they shouldn't -- then I think you have an
obligation to damage it whenever and however possible. Separate the grain form the chaff, as it were.
Some Christians like to say that anyone who deconverts was never really a "Christian" in the first place -- there is some truth to that, but not in the way they expect:
Contrary to what they say, nobody turns away from Christianity because of evolution -- they turn away because they've been lied to (either unintentionally or... not) by those whom they trusted about what Christianity was about in the first place.
If they were taught, "to be a Christian, you MUST accept
X,
Y, and
Z, as the Truth," and then later find out that X, Y, or Z doesn't sync up with reality, then of course they're going to reject it. The truth is that Christianity is ridiculously simple -- believe that Jesus Christ was the Son of God who died for your sins. Period. Full Stop. If X,Y,and Z aren't about that, then what they've been taught isn't about Christianity.
Evolution, like many of the scientific discoveries before it, is simply the latest thing that exposes the Xs,Ys, and Zs for what they are -- unnecessary frou-frou and window dressing at best, a stumbling block for honest seekers at worst.
Get rid of it -- go back to basics. John Shelby Spong said it best: "Any god who can be killed ought to be killed -- and any god who must be protected from truth, form any source, is dead already."
Does a Christian need a young Earth to believe in Christ? Do they need a literal six-day creation or a global flood to think they're saved? Do they need you to think so, too?
If yes, why?
If no, then what are they fighting for? They're just... fighting.