The danger for Bulgaria is precisely this. The EU is already making noises that countries like Bulgaria have an ageing population and a shrinking workforce and both these are happening because Bulgarians are seeking work in other countries. A similar noise was made in western European countries immediately prior to mass immigration being forced on them.
The situation in Europe is now this. Germany has invited anyone who wants to come into Europe and has found itself inundated with more than a million people (with millions more on the way) , many of whom are causing serious social disruption and who are costing the country billions. Germany now needs somewhere to send the excess migrants and the EU will force countries like Bulgaria to take them because the workforce here is declining while the age of those left behind is rising.
The solution to these problems is to encourage Bulgarians to return to their own country and that will only be accomplished by removing corruption here and paying Bulgarians decent salaries. Look what is happening in the west - does anyone seriously want that repeated here?

History is a science. It is not a “story” to use in propaganda to fortify our children’s tribal prejudices. As with any science new discoveries shine new light. This upsets some people who fear and hate any truth that threatens their view of their tribe or other tribes. The level of upset is often violent with those involved in the research being subjected to vicious and violent attacks. The level of danger to researchers who discover uncomfortable facts depends on the society and its stage of development.
The men and boys who died in Srebrenica were not killed by bullets they were killed by the poison that their killers learned at school. The failure to teach scientific history can be found all over the world. Chinese money is adorned with the face of a man who killed 38 million Chinese. The Americans have the face of Thomas Jefferson a slave owning pedophile who supported the “removal” of the native population on their currency. In Russia they are dusting off the statues of the Georgian Monster. In Belgium Leopold II still sits on his horse.
In Bulgaria it is not possible to honestly teach history and it will not be possible in a generation. A people who cannot face the past is a poor people. Bulgaria’s death rate is the 8th highest in the world. Afghanistan, war-torn for decades, is seventh. Somalia is ninth. The countries in the top 7 have gone through sustained armed conflict, famine, genocide, apartheid and a nuclear disaster. Bulgaria went through 26 years of Bulgarian Rule. As of 2015, 2.5 million people born in Bulgaria work outside the country. The workforce will fall by another 50% by 2050. Criminal gangs run the country and the educated class languish in underpaid despair while their children emigrate. There were bad Sultans but few as bad as this.
You say scientific history is “to make people believe that other cultures are superior to their own so they would not complain when their country was taken over.” This is the kind of thing being preached by our reinvigorated extreme right wing people. No scientific historian preaches superiority and nobody has been “taken over”.
The great irony is that the people who would agree with you in the West do not want Bulgaria in Europe and consider you inferior. But then again Bulgaria fought for Hitler and he was planning to sterilize the Slavs. So nothing new there. Bulgaria's Nazis allies had a policy towards Slavs which was to exterminate, ethnically cleanse and enslave them. In order to deviate from this for strategic reasons in the case of Bulgaria Hitler decided that the Bulgarians were not Slavs but Turkoman. That is the great thing about nonscientific history, it can be rewritten by any fool to suit his purpose. Thankfully the real history of the Bulgarian peoples is written in their genes and no dangerous fool can change that no matter how inconvenient some people may find the story that the genes tell.

This revision of history has happened in western europe and has resulted in at least 2 generations of school children having no respect or loyalty towards their own country - the country their ancestors built with their hands and their hearts - and sometimes their blood. The revisionism was done as a precursor to force multiculturalism onto these countries and to make people believe that other cultures are superior to their own so they would not complain when their country was taken over. Anyone who did complain faced backlash from their peers and from authority sometimes resulting in arrest. This should not be allowed to happen in Bulgaria