Defending language and human expression by arbitrarily limiting the scope of what should be considered valid language and expression.
The linguistic niche that emojis fill is the same niche that is filled by emblems, which are a powerful tool for communicating specific ideas very concisely and have existed long before the internet. If pictures are too childish and regressive for this guy, then I suppose they want a world without bright red hexagonal stop signs and railroad crossing markers and would instead prefer traffic control markers be replaced with plain text billboards containing the relevant legal codes written in plain text.