The difference here is that Crimea was poor, but Russians living in Estonia actually have a good life. They like to make noise, but all of them know very well how much better they have it in Estonia than Russians across the other side of Narva river.
I don’t know too much about military things, but here are my thoughts: There are no Russian military bases in Estonia as there is in Crimea and there is a visa regime. On land their military could get to Estonia over the bridge of Narva river. Border check is not heavily manned so maybe they manage to get some of their forces over the bridge before it is destroyed and bring other forces by other means. That would certainly mean invading a NATO member.
here in Poland I have a friend who is half-Russian, half-Estonia and he seems proud of both sides, but he is very much a libertarian and dislikes Putin (interestingly he's engaged to a half-pole, half-ukrainian :-P)
We're also close friends with a lady who is half-lithuanian, half-russian -- I've not asked her about her opinion yet.