If that's your idea of a "mild" one what would you regard as religiously offensive?
This is true of many religious words used in this manner ... they've pretty much lost any bite they once had. E.g. "God! <complain complain>" is similar: 75 years ago maybe you'd have had people up in arms over that, but these days nobody will even notice.
Clearly 2 people on this forum alone have already noticed.
And you're right: it has everything to do with the reaction it gets. Many would disagree about your characterization of it as being "mild," or whether it's "lost any bite," and there's the rub: whether or not that's correct is up for debate, but I'd also submit that it's largely irrelevant whether or not that is, in fact, as inoffensive as you believe it to be.
While you may not think it offensive, many do, and would consider it a thoughtless treatment of something that's important to them. We can all argue about whether or not that's reasonable, but it's the reality, nonetheless.
It's one thing if you know your audience, but it's another thing to be commenting in a public place.
Consider this variation:
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It has nothing to do with what I think, it has to do with the way the phrase is typically used, and the reaction it gets: In normal usage, it's mild.
This is true of many religious words used in this manner ... they've pretty much lost any bite they once had. E.g. "[racial epithet/gay slur/nationalistic slur/etc.]! <complain complain>" is similar: 75 years ago maybe you'd have had people up in arms over that, but these days nobody will even notice.
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I'm sure inside those brackets there are plenty of things I could say that wouldn't feel offensive to me, or even many of the people I'm around in the real world, but if I care about making my point without it instantly becoming about how I made my point, then I'm probably not going to start my comment off with something completely irrelevant to my point that runs a non-trivial chance of offending someone who reads it.