To make my opinion clear, I think one should keep at most one blue gourami in a tank that small. Not two, not three, not any other number. It's better to just stick with just one than get several and take the risk of getting an especially aggressive one. If it happens to be an aggressive one, things won't end well and I don't think it's worth the risk, based on my experience and the experience of others.
I know someone who kept blue gouramis in a 300 l (what's that, about 75 gal?). During spawning season, the male took over 2/3 of the tank and wouldn't let any other fish near. What if these fish in a 28 gal happen to spawn when the owner is away and can't destroy the bubble nest? Dead bodies for sure, methinks.
I do know about the behaviour and mentality of gouramis, I've had quite a few of them during my fishkeeping time. I know a pair is definitely out of the question, as you said, as are several males. I also think that since blue gouramis grow so big, there just isn't enough room for a relatively stress-free life for 3 of them in a 28 gal, especially if there's a male involved.
You can stand by what you said if you like, and I'll stand by what I've said. In the end, the decision is up to the person asking the question.