Here's hoping the OP is reading...a similar, but not quite the same, story may help.
I empathize completely. I grew up in the same part of the country and wonder if the in-laws were like mine.....generations rooted in the church and steadfast in tradition. And the traditions and beliefs were no alcohol and no discussion of it. Wrong. Period. No wavering because that's the way it had been for generations. They were well known to bash even a teetotaller. Deacons and leading church figures were they. And that was only the beginning of the different beliefs. I was raised in an environment of exposure to alcohol from the first memories of family gatherings. My family was those "damn yankees."
I was fortunate enough to begin dating my wife before we could legally drink, or illegally for that matter as it was a dry county and our bootlegger would not sell to minors. I then proceeded to corrupt her with alcohol as she moved away to college and out from the disdain and intervention and became aware of the rest of the world. After several years together (some spent in cohabitation unknown to the in-laws) we announced a marriage. We had two ceremonies and two receptions....one at her grandparents (grandfather was the longest serving deacon in the church and the preacher was his best friend and frequently at their house when we would visit) with cake and tea and limited guests and another across town at my parents.....WITH BEER!!!!! When we announced our intentions, we learned there had been lots of discussion about our relationship within her family but no one had ever approached us about it. Being out of town probably helped that considerably and with lots of people around at family gatherings, it would not have been "proper." Interventions are not things they do but talking about them is. We also were told that I had gained respect despite the fact that they knew I drank....I did not flaunt drinking, nor did I profess any dislike for any beliefs opposed to it.
We invited the in-laws to my parents with the full revelation of drinking and revelry...they chose not to attend and only then did they comment on the drinking and say they could not attend such a function. And I truly believe that it was not their opposition to the drinking but their fear of what the rest of the brethren might say. They considered themselves role models and that required exemplary behavior. In my years of growing up in Middle Tennessee, I learned that was the biggest motivator among many and was so prevalent that one had to learn to respect it as a way of life. Not like it, but respect its dominance.
We went years with limited visits, both parties choosing to let sleeping dogs lie. I know this bothered my wife. I finally decided to kick the dog. I invited them and broke out a beer and also revealed the homebrewing. I laid all the cards on the table and reminded them they knew for years that I drank, that I had never been drunk around them, that I respected their beliefs and had not even drunk alcohol in front of them and that we had not been destitute or homeless or lacking because of the money spent on my hobby, which I wanted so desperately to point out was significantly less than what they spent on cigarettes............I asked for the same respect that I had earned earlier be extended to include my homebrewing. I had earned the right to marry their daughter. Did I not have the right now to take care of her without intervention? But should I feel the need, could I count on them for advice when I sought it? And if they did truly feel that a problem was developing related to beer and/or homebrewing that they should approach us and we could have reasonable discussions. And if someone criticizes us or them for anything related to beer, then perhaps they should simply remind them of the good things we do and ask rhetorically if the other party would not agree that we are basically decent people and the beer should not be our sole judgement? After all, let he who is without sin cast the first stone........
A calm, respectful, not defensive but appealing to their love and respect discussion worked. I never heard another word about it. Sadly I had hoped for loftier goals; actual inquisitiveness. But that didn't happen. I still consider that a little lack of respect but one I was willing to trade.
Good luck.