The following is founded on basic game theory; I think I've given a good explanation here, but if not, feel free to take it to my inbox. In-depth explanation is just a bit
off-topic for the thread, but it's kinda important when it comes to ethical theory.
Because a significant chunk of human interaction, this included, is essentially iterated Prisoner's Dilemma
. At any juncture where you're trying to coexist and share anything - including, say, public space, a voice in your nation, rights and freedoms - with your fellow person, you can choose to cooperate - in which case everybody gets most of what they want - or betray. If you betray and the other guy cooperates, you win everything and they get nothing! If both of you betray, well, then it's an ugly fight to see who can grab what, and nobody winds up with as much as they would've gotten with either of the first two options.
Given this situation, we obviously need a way to punish those who betray, who try to seize everything. If we always
cooperate, then the first untrustworthy party we meet will take us for everything we have, and eventually kill us off. Not a good ending. Unfortunately, the only thing we can do is betray in kind. This leads us to what is pretty much the optimal solution - tit for tat. Cooperate in the beginning, then do whatever the other guy did last time. If both sides approach the problem like this, then it's a very stable state of cooperation! Everyone wins! If one side betrays, they know things are going to go downhill fast - betrayal might be a short-term win, but in the long term they'll get far more out of just cooperating and coexisting. A cycle of betrayal needs one party to break the tit-for-tat ploy - to trust enough to cooperate again - but then it immediately snaps back to a stable state of cooperation. This doesn't always hold - if one side is overwhelmingly more powerful than they other and not bound by other constraints, "betrayal" can take the form of war, genocide, or purges that completely destroy the lesser party - but in general you can expect it to be true.
So how does this apply to Russia? Well, we have two parties - LGBT people and hetcis folks - who have, more or less, cooperated for twenty years. Now one side has betrayed - tried to legislate away the rights of the other side. If LGBT folks cooperate and say "That's okay, be as intolerant as you want! We accept that!", then there is exactly no incentive to hetcis people to stop the oppression or prevent it from getting worse. We need a disincentive - it's time to betray in kind, to reject that intolerance and call it out for what it is, to stand up.