Only legitimate crazy people here would have a problem with the sentence “All lives matter.” People have a problem with the slogan “All Lives Matter”, which was made in reaction to “Black Lives Matter”.

I don’t know if you are ESL if you aren’t American but the capitalization I used matters and it’s difficult to explain the context of hearing a sentence vs a slogan. That’s also before you get into people specifically trying to conflate them so they can do a sort of motte and bailey type argument by claiming they weren’t saying “All Lives Matter” just that “All lives matter, so they can uno reverse you as the bigot