Charlie Brown you are putting apples and oranges together. Classic of the left and their ignorant followers. First off to tell someone who owns a business and provides a service that they must preform that service I.E a cake with something they disagree on is not the same as providing a public platform for communications and then telling people what they have a right to say and not say is not even in the same ball park, not even the same game.
If someone is a photographer and does not want to be part of a gay wedding, there should be freedom of that person to decline based on their beliefs. What you are saying is the same thing is like ATT saying we don't like this group so we will not let them use our telephone system.
This can cut both ways in that if someone does not like blacks they can say I don't like burn loot murder so they can not use my electric service to power their printing presses. There are degrees of separation. In one scenario you say that making someone participate directly in the thing they are against or is antithetical to their belief system is the same as someone using your product to produce a thing or spread an idea you do not agree with. not only this but your question cuts both ways. If you are saying people have the right to cut off anything they own for use to someone who they don't like or agree with, then you must say that any one can deny anyone anything if they so choose. So we are back to the Woolworth lunch counter.
The owners of Fuckbook and Twit provide a platform for others to set up their own space. Like leasing someone a space in a mall. Unless they are doing something illegal its not up to you to tell them what they can and can not do or how they can do it, just because you may or may not agree with the idea. A better analogy would be you make a product that decorates cakes. You will not sell to anyone who uses your decorator kit to make gay cakes or anything that is against your ideology. You are several degrees away from actually being involved in the end product. Unlike the person who makes the cakes or caters the event.
There is a huge difference in telling someone I will not put have a great rump ranger wedding night on a cake and selling a blank cake and the person who bought your plain cake puts that logo on it. The cake maker should have no control over what the thing is used for one its in the hands of the user. That is their responsibility.
We see this twisted logic used by the left and their useful idiots all the time. The left wants to make gun manufactures responsible for the misuse of their guns. this is like telling GM they are responsible for an accident because the Corvette involved was designed to go faster then the speed limit. But logic and Liberals are in fact antithetical.