No, it is not appropriate at all. Such stories involve private and sexual content that should be kept within the boundaries of a private and consensual relationship. Sharing this kind of story in public violates privacy and is not in line with good social ethics.
This is a very personal and inappropriate topic. We should focus on positive and healthy aspects of the gay community such as their rights, equal relationships, and contributions to society.
I'm not sure specifically what a 'first time cum swallow story' would be in a general sense. It could potentially refer to a very personal and private sexual experience which is inappropriate to discuss in detail. However, if it's used in a more euphemistic or non - sexual way, like the first time swallowing a difficult - to - swallow pill or something similar, that would be a different story.
This is a very inappropriate and vulgar question. Such behavior is a personal choice and can't be generalized or discussed without considering individual circumstances and values.
One way is to set clear boundaries in conversations. If someone starts to tell such a story, firmly but politely indicate that it is inappropriate. Also, promote positive and respectful topics in social gatherings.