I have heard that we should not drink milk products after we drink the xxx rum or whiskey. I'm not sure. But curd and buttermilk is always in my dinner. Can you make it clear? What happens in the stomach when milk products and alcohol meet?
The acidity (ph) of ethanol is relatively neutral (roughly equivalent to water), so milks and creams will typically mix fine with ethanol. In fact, it's the basis of many popular alcoholic beverages, like and "egg nog" (which is a spirit, a whole egg, cream and simple syrup), or the White Russian (vodka, coffee liquor and milk).
Milk or cream-based beverages can become curdled, but it requires a high level of acidity (e.g. lime juice) to be introduced prior to consumption. It's why the "cement mixer" shot becomes curdled (the combination of cream in the "Irish Cream" and lime juice). If you are not familiar, do not try to drink a cement mixer "shot", it is typically considered a really bad prank to pull on an unsuspecting victim. https://en.wikipedia.org/wiki/Cement_Mixer_(drink)
Even though butter milk is slightly more acidic than regular milk or creme, it's not enough to cause a reaction like curdling (unless you add the aforementioned high level of acid). Plus, milk already curds somewhat on its own in the stomach.
There is a popular myth that drinking buttermilk (or regular milk) prior to alcohol consumption has preventative benefits (i.e. "hangover cure"). However, there is no scientific evidence that supports the claim that drinking any type of milk (even buttermilk) before consuming alcohol does anything to stave off or reduce hangovers.
Conversely, it is well known that alcohol consumption slows digestion and reduces absorption of nutrients, especially those found in milk. This is because the alcohol reduces the secretion of digestive enzymes, which are what breaks down food in the stomach, including milk proteins and sugars. Alcohol also increases acid levels in the stomach, but it doesn't typically cause major negative side effects, when consumed in moderation, unless there is already another medical factor present.
High levels of milk or creams, followed by excessive alcohol intake can produce effects similar to lactose intolerance, because the milk sugars are not digested well and move into the intestines. Once excess sugars are in the intestines, the bacteria there consumes the sugars and produces large amounts of gas. High levels of sugar in the intestines also causes more-than-normal amounts of water to be drawn into the intestines...a.k.a. "diarrhea".
As long as you aren't eating cheese curd sandwiches, made with flourless (i.e. all-cheese) cheese bread, with 5 slices of cheese and cheese soup, followed by high levels of alcohol, you should be fine. Moderation with all things is the key.
Note: If you are diabetic, you run the risk of much higher levels of milk sugars going into the intestines and should consult a physician, because prolonged sugars in the intestines and stomach can lead to gastritis or even ulcers.