The pressure group West Country Respect demonstrated at the Recreation Ground yesterday - although there was no home game at the time.
Twenty Respect campaigners held placards which spelt out the words 'Nice People Take Drugs' - the theme of a campaign launched earlier this year by a separate group, the national organisation Release.
They say the rugby world is "hypocritical" for cracking down on drugs while heavy drinking remains part of the sport's culture.
Five Bath Rugby players have left the club in recent months as concern over drug-taking in the sport increases.
The most high profile case was that of England star prop Matt Stevens, who quit the club in March after admitting a cocaine habit, while Australian Justin Harrison left at the end of May after admitting he took the drug at an end-of-season celebration.
Three other players - Michael Lipman, Alex Crockett and Andrew Higgins - ended their contracts after being accused of refusing to take drugs test following the same party in London. All three denied taking banned substances.
West Country Respect was set up to "protect the health and defend the rights" of people who take drugs, and says the rugby club has been unfair to the players involved.
The national Release campaign aims to get over the message that all sorts of people get involved in drug-taking and to challenge stereotypes and stigmatisation.
In a statement, Respect said: "Fed up of hearing that drugs are bad and that by extension people who take them are bad too, Respect have invited people who use drugs, their friends and families to speak out against the unfair treatment of people who use drugs.
"We want our rugby players to play well, we don't care whether they use drugs or not. Bath Rugby is being hypocritical telling us that drugs are bad when heavy drinking is so much part of rugby culture."
"Matt Stevens' experience indicates that if someone is found to have a problem with drugs then they will face a ban that could end their career. This is no way to help young sportsmen deal with the pressures of operating in the modern professional era."
Spokesman Mat Southwell added: "It's wrong to equate drugs like cocaine or cannabis with performance enhancing drugs. We don't support Bath Rugby's decision to hound good quality rugby players away from our team for taking drugs."
He said after the protest: “We think that the way Bath Rugby Club have acted towards players like Matt Stevens is wrong.
“He has been punished for his drug problem, instead of helped.
“His career has been ruined, when all he needed was some help and advice on how to overcome his addiction."
Bath Rugby has not commented on the protest.