Vegans are barred from entering pubs during the Boxing Day hunt, which leads to counter-attacks on social media.
Some people accuse The Dorset pub in Lewes, East Sussex, of being "discriminatory".
Harvey's, the brewery that owns The Dorset, said it was "shocked", and an employee had been suspended for "inappropriate" marks.
Sussex police were summoned when clashes broke out between those who took part in hunting and protestors.
According to the menu, the pub on Malling Street serves vegan and gluten-free customers, and that is only during hunting when a sign appears in the window.
On Twitter, Gilly Smith said: "Isolating and discriminating against their own customers? Really smart marketing methods. Must be ashamed of themselves and boycotted."
A spokesman for Harvey said: "Following the comments generated by [the] posters that are inaccurate, insensitive and inappropriate, the company wants to issue a formal apology for any confusion, violations or annoyance that may arise.
"Harvey disagrees with the sentiments of this sign in any way, and is shocked by the inconsiderate actions of the individual concerned … [an] the employee has been suspended while awaiting an ongoing investigation.
"Harvey & # 39; s fully committed to the inclusiveness of all guests. We … want to convince customers now and in the future that all are welcomed at our place. This will not happen again."
Dorset disabled his Facebook page after the photo was shared more than 100 times.