If we replace all plastic cups with glass cups, might we get micro-glass inside ourselves instead?
Glass, mostly silicon dioxide, might sound harmless, but glass can chip off in microscopic sharp fragments (think fiberglass dust - which some suggest might be as bad as asbestos). Glass also slightly dissolves in water (this is how glasses start to look frosty after enough dishwashing - they're dissolving), and slightly evaporates (everything has a vapour pressure!). And obviously the glass isn't pure - there can be all kinds of deliberate and accidental additives.
Am I worried about glass? No. But it seems naive to wholesale replace plastic with something else until there is a decent understanding of the replacement.
Also, while glass does dissolve in water, it is an extremely slow process that does not affect containers at room temperature in any significant way. As for the claim about glass evaporating due to vapor pressure, while technically true, the vapor pressure of glass at room temperature is so infinitesimally small that it's completely irrelevant for practical purposes. This process occurs at such a slow rate that it would take far longer than the age of the universe to have any measurable effect on a glass container.
How about we leave the silly accusations of malice at whatever low rent other website they were learned at. You don't know motivations.
I definitely feel we should be more serious about reducing use of plastics, especially for uses likely to contribute to microplastic levels, but it’s going to be hard to convincingly make that case without quantifying these risks in relation to actual human microplastics levels.