Well, as usual, it's more complex. That account is what he writes about just one campaign into Bulgaria.
As a tangent, BTW, he actually writes a breakdown by province of how many killed, not just the total figure (which you may notice isn't rounded up or down), so if he's exaggerating it, he's doing a very credible job of it. It's essentially a cold-blooded spreadsheet (so to speak) of numbers of people killed, and it adds up. So it's also not very incredible that he'd not just do it, but also keep an OCD-kinda record of the mass murder.
And yes, supposedly in that campaign he impaled the Muslims and at least claimed to relocate the Christians. Which is why he was such a hero of Christianity for it. "Love thy neighbour" apparently only counts if thy neighbour is Christian, and the right shade of Christian at that
Exactly how he separated them, that's anyone's guess. I mean, if someone asked you if you're a Christian or about to be gruesomely executed, dunno about you, but I'd take the first choice.
But to return to it, that's not the only instance he impaled people or where he's accused of killing people. Doing it to the Turks doesn't preclude also doing it to his own people too. The two don't really exclude each other.
That said, as a further correction, his own people were not Slavic. The Wallachians were a predominantly Latin population. The people in Bulgaria on the other hand, WERE predominantly a mix of Slavic and Turkish. So that campaign was predominantly aimed at people of another nationality than his own, one way or another.
The Slavic sources that glorify him are basically Russians, not his own subjects.
Also when he says peasants, he probably means it. Not only really he didn't have the time to siege stuff, but his raids in Transylvania also completely bypassed fortified stuff and killed unarmed peasants before anyone could react. So it kinda fits the pattern, IMHO. He probably did kill peasants, not some ruling class or even burghers.
To further complicate any analysis of his personality, is that the guy was IMHO about as stable as a mixer full of nitroglycerin.
He didn't just trick his Turkish liege. He sought protection from Matthias Corvinus of Hungary (which included the duchy of Transylvania), but raided his border lands. Vlad's cavalry helped put Stephen The Great of Moldavia on his throne, but Vlad's troops later gave Stephen the leg wound that would infect and eventually kill him. He may or may not have killed the elite guard that Stephen gave him to keep him alive in his second reign; it's not very clear, but it would be crazy enough to be credible for him.
You get the idea. It's kinda hard to guess what was going on in his head, because he was acting very unpredictably. Which, granted, served him well in warfare.
So I was wondering how he could curry such support while torturing lots of innocent Slavic peasants. 
