despite myself hearing about the event for the first time today.
That might be a good place for us to wrap up but no, it doesn't agree with you since you seemed to think it happened after communist rule and had something to do with perestroika. Neither of these are true. The lack of familiarity is hardly some mortal sin but it puts you in a very poor (while undoubtedly easily correctable) position to assess the repressiveness or lack thereof of the Bulgarian communist regime.
It happened in the middle of the transition period between uncontested communist rule and EU's unicorns and rainbows, and was not characteristic of what communist period's steady state looked like. It was characteristic of its failure modes, I would not contest that.
The fact that you've used this transition period event as your prime example suggests you cannot solidly back up your claims about communist period.
I am ready to be corrected but you will have to actually make your claim.
In case you water it down to "simple" forced assimilation: so did Denmark (in Greenland) and France and of course Turkey. If they'll all repressive by your standards then all right - not the worst company to be in. If only socialist Bulgaria is repressive to you then you're employing double standards.
In fact, it would be interesting to hear your assesment of Turkey v.s. Bulgaria W.R.T. repressiveness. Kurds et al.
It happened in the middle of the transition period between uncontested communist rule and EU's unicorns and rainbows
It didn't. I don't know where you got that idea, it's not borne out by anything reasonable you can read about it. The relevant Bulgarian expression (with an appropriate side of Turkish) is хал хабер си нямаш.
"Big Excursion" happened in 1989. Berlin Wall fell in the same 1989. Does it ring any bells? I'm not sure why one would claim stuff happened in a Second World country in 1989 is not a part of its transition period. Ethnic cleansings in Yusgoslavia and ex-USSR republics were also nigh or already started to happen.
I'm still apt to hear the comparison between repressiveness of pre-1989 democratic, capitalistic, NATO member Turkey and that of pre-1989 socialist Bulgaria.