If two adults wish to engage in intercourse together, then there should not be anon who i trying to stop them. Consenting adults that understand the terms of a relationship should be allowed to do so, as well as assuming any risk of either getting pregnant or a Sexually Transmitted Disease.
Sex is appropriate on the first date if things go really well and both people hit it off right away. Both partners could be completely vulnerable at the time and simply want human companionship and intimacy. However, if both people are consenting adults and feel like they are in tune with each other, there is nothing wrong with sex on the first date.
Having sex on a first date is not acceptable. Sex is supposed to be an expression of two people who love each other, not just someone fulfilling their sexual urges. Sex is so casual these days that it is no longer considered sacred like it was intended to be. People should at least know each other before they engage in sex.