Bacon Bits
Legend
I'm going to disagree with this one, but simply because of the fundamentals of the language. In English the male gender (in the original literary sense) is considered proper use when referring to a mixed group. For example, "man" and "mankind" refers to all people, regardless of sex or gender. The problem is that the term gender has changed from being just a literary term to being somewhat synonymous with sex, creating a level of confusion between the two uses.
I wouldn't say "is" at all anymore. I don't believe APA or MLA or Chicago support this grammar anymore. I think they all support "they" as the neutral pronoun today.
It certainly was true in through the mid 90s when it started to get real pushback, but 1e and 2e authors could rightly claim it as the preferred and accepted style of the day. However, "he or she" was also very common in the 80s and 90s, in spite of how awkward it becomes after repeated use.