Should there be notices of any nature in pubs or other places the question you have ask is "WHY". Pubs, like shops, stores, offices, banks, manufacturing plants etc.,etc. are there to make a business and a living for those owning or being employed in them. If, as result of bad experiences or regular dis-ruption, by particular groups, the owners find their businesses are compromised, their long term regular customers are leaving in droves and their finances are being drained through falling income then surely they have the right to exclude those that they deem to be responsible for the decline in trading.
          There are certain pubs that have been obliged to exclude football supporters because their noisy, un-ruly behaviour, and foul language has driven away local clientelle which the publican would like to see all year round. This is just one example.
          I repeat, the question is "WHY". If your answer to that is "because they are fascist racists etc." then you are not giving reason a chance.