This isn't exactly true. Plastic is all different types of things and there is no one melting point, for example PLA (poly lactic acid) which is commonly used for things like disposable drink lids has a glass transition temperature of 60c (140f). Abs (acrylonitrile butadiene styrene) has a glass transition temperature of 105c (221f).

While the full melting point for these two polymers is higher than the glass transition, at those temps, your straw will start turning into a nice wet noodle.

The melting point isn't helpful here because it defines the point at which the object turns into liquid, not the point where it deforms or gets damaged.