I certainly don't agree that everyone with IBS must avoid all alcohol. There may be some adult beverages you can enjoy in moderation. Let's really zero in on FODMAPs.
People with IBS who adopt a plant-based diet can expect to have more trouble with their symptoms if they are FODMAP-related.
Most people can easily meet their protein needs with food alone on a low-FODMAP diet, but sometimes a protein powder is called for.