I didn't comment originally for reasons that have been covered.
With the new direction, I will offer this. A message board can be a great way to practice that polite confrontation, because you can take a moment to compose your thoughts, type a response, reread and edit (repeatedly as needed), and only when you are satisfied do you need to share the response. Unlike IRL when you usually have about 1 second to respond. So this can be a great training wheels environment. But that is going to work best if you tend to take all the steps I mentioned, especially at first.
For the lady at church, I'd likely go with one of my standard responses. (I too am anxious, introverted, and inclined to avoid ALL confrontation, even when it is not healthy or helpful to do so. So I find what have a few standard scripts serves me quite well because I don't have to think quickly.) In this case, I'd likely start with the very easy but very effective "Why?" That's it. She says we need to talk less about LGBTQIA+, and I turn to her and with no meanness in my tone just say, "Why?" If forces her to see that her thought is not universal, nor is it going to be given a pass. It also usually forces her to articulate the icky thoughts that lead to the comment, which often has the effect of making sure everyone sees how icky they are, without me having to do the heavy lifting to get them there. If she demurs with "oh, you know" or "never mind" or similar, a "No, I really want to know and understand. Why do you think we need to 'tone down the LGBTQ stuff?" Again, it doesn't let her off the hook, but it also doesn't require me to be especially confrontational. Depending on her response to that, I might state why I disagree, or let it go if she's already shown her ass sufficiently or has retreated, or take some other approach as necessary. But the "Why?" gets it started without me having to think on my feet, and often leads to somewhat of a resolution (as much as such a thing can be resolved) without me having to come up with a perfect response on the fly. Overall it is an effective strategy/response and one that works very well for my conflict-averse personality.
Similarly, "why is that funny" is great for most offensive jokes.
And the larger strategy of just having a few canned responses that you can go to even when you are anxious and frazzled may be really helpful for you, especially when all this is new. It's incredibly helpful for me, and many different situations. Of course you can't be prepared for every situation you might encounter, but you can be for many of the most common ones.