In the US, more than two centuries of jurisprudence holds that commercial activity is not speech, and is thus is not generally subject to the protection of the Constitution. Moreover, the Constitution explicitly gives Congress the power to regulate Commerce.
Doing business thus is validly subject to government regulations mandating that businesses do (or not do) certain things. And some of those things include not discriminating against the disabled, and designing your business facilities to accommodate the disabled.
Given that commercial activity affects my unalienable rights to life, liberty and property I would disagree that its not subject to the protection of the Constitution.
I also find fault with the commerce clause of the constitution and think its broad interpretation as an economic defense mechanism is archaic and filled with undesirable effects (such as the drug war, limitations to trade and international tariff wars), not to mention contradictory to the constitutional principle of liberty.
Your personal interpretation disagrees with the Constitution that actually exists and with the two centuries of legal cases on constitutional rights.
The Constitution was intended to give the government broad powers. It was written in reaction to the Articles of Confederation, which created a government with limited powers that failed with 5 years. The provisions of the Constitution and the bill of Rights need to be understood within that context.
Its not my personal interpretation, and just because legal cases interpreted a certain way for two centuries does not make them right. The constitution was not intended to give the government broad powers, but rather to assign limits to its scope. The context in which it "needs to be understood" is not for you to define, but up for interpretation.
"The United States Constitution presents an example of the federal government not possessing any power except what is delegated to it by the Constitution — with the Tenth Amendment to the United States Constitution making explicit that powers not specifically delegated to the federal government are reserved for the people and the states."
Doing business thus is validly subject to government regulations mandating that businesses do (or not do) certain things. And some of those things include not discriminating against the disabled, and designing your business facilities to accommodate the disabled.