Dear Customer (name blocked for privacy),
It is often said that freedom of speech does not mean all speech is protected and some organizations, such as a company, whether for profit or not, may be allowed to restrict it in certain ways and in certain cases.
The US courts have, principally, protected most stringently the freedom of speech for religious or political reasons, but other types of speech, such as profanity for profanity's sake (but, if profanity is used to express a political thought, such as the Vietnam era case where a court kicked out a man wearing a "F--- the War" shirt and the Supreme Court later said that because it was a political statement the court had to allow it); commercial speech; etc. is not so protected and may be banned or fined in certain cases, particularly by a private entity, such as an association.
For example, the following article regarding fines by the FCC for indecent language speeks about this topic. Notice that the ACLU here is NOT saying the FCC has no right to ban or fine such language, instead, it is saying that the FCC must specify exactly what language is considers indecent and when in order to constitutionally have such a ban. https://www.aclu.org/freespeech/gen/11529prs20041111.html
Information on the First Amendment and its purpose/scope is also available at the following websites:
http://www.uscourts.gov/outreach/topics/firstamendment/speech/background.html
http://faculty.ncwc.edu/toconnor/410/410lect08.htm - this provides a nice summary of the right to restrict speech in certain cases
As you can read above and in the links, while it is not accurate to say that all speech is protected, it is also not a clear cut case of when or where a violation of the First Amendment may occur without first conducting a full review of how such restriction is written; how it is enforced; how much speech it restricts and why it restricts such speech; etc. This is something you may want to contact the ACLU about to see if they can help you determine, based on all of the facts you have, whether a potential violation may have occured. - http://www.aclu-sc.org/
PLEASE NOTE: Responses here are for information/education only, NOT legal advice and do not form attorney-client relationship! Only licensed attorneys you hire in your state can provide legal advice.