There are so many things just plain dumb about this meme, I'm not sure I can count all of them.
See, now the funny thing is, liberals don't generally make a big fuss about things like that, even if there was an equivalency, which there kinda totally isn't :)
As Nate McD says:
Liberalism is a political philosophy or worldview founded on ideas of liberty and equality.
An enemy of that would be opposed to the liberty and equality.
And, yes - my "opinion" is that the premise of forcing people to put a symbol of rebellion against lawfully elected government, a symbol of white supremacy and institutionalized enslavement of human beings on a cake, is not equivalent to denying service to someone on the basis of skin color, sexual preference, being the "wrong kind of" Christian, or whether they love guns.
Funny thing, that.