Yes, and people that challenge the science who then become scientists actually research/experiment thenselves. They don't go and claim science is false until they have actual reason/evidence to believe so. One can question science all they want when they do their own science on the matter and it isn't handily disproved beyond reasonable doubt by existing evidence.

Most science deniers do not do that. Making anti-science claims without obtaining solid, consistent evidence is not science.

"There's no law against it" is a laughably stupid reason to do something. They're free to do it but everyone else is free to acknowledge that their uneducated/misinformed skepticism is harmful to society and that their opinions are meaningless to those who aren't dumb. Leave the contemporary science denial to those who actually somewhat know what they're talking about.