Changes in language are not bad grammar
Language changes and evolves over time. We don't speak the same English today as our ancestors spoke centuries ago; we don't even speak exactly the same English as our parents and grandparents did. Language adapts to suit our needs in the here and now. Sticking to outdated rules made ages ago only impedes progress, as we can't talk about new and current facets of society with only the language of the past. One example is singular "they." According to many grammarians, "they" is strictly plural. But many people use singular "they" to refer to someone whose gender is unknown. The grammar is changing; but this isn't the first time it has changed. It was once used exactly as singular "they" is used today, but grammarians complained and it was changed to be plural only. Now, it is changing back to what it once was. It is changing even further to be used as a gender-neutral pronoun for non-binary persons. Another example can be found in tech terminology: Humans did not have computers a hundred years ago. The word "computer" existed, but it meant "a person who computes." The word had to be changed and adapted to define something new. Current trends and issues create a need for changes in language. If we stick to archaic rules and definitions, we are cutting ourselves off to new meanings and possibilities. Grammarians need to learn to accept that as times change, the rules of language need to adapt.
Grammar does not need to change in order for new ideas to be expressed. We can create new words or adapt old ones, but the grammar itself must remain the same in order to maintain the structure and integrity of our language. The rules of grammar are put into place for a reason: to ensure clear and effective communication. Changing the grammar will only lead to confusion and a breakdown of students' ability to write.
[P1] New facets of society sometimes call for updates in the way we use our language. [P2] Changes in language should not be considered bad grammar.
Rejecting the premises
[Rejecting P1] We do not need to change grammar to express new ideas. [Rejecting P2] New or adapted words are fine; but when someone uses bad grammar, it is not a "change," it is an error.