But it isn’t, and it fits in line with the Civil Rights Act Title VI which prohibits businesses that work for the federal government from discriminating against certain classes. This is the same law, but at the state level. Speech is not curtailed unless you choose the option that requires curtailment.
Like I say, the business is free to not take state contracts then refuse business to whoever they like (just like the gay cake baker did), but if they want to work for the state they have to follow state rules.