Consider this: The procedure they use to remove the fetus during an abortion is the same used to clean out after a miscarriage. Plenty of people go on to have healthy pregnancies after either.
That is extraordinarily rare. The statistic is very low and I think you are right to be skeptical. What does the infertility stem from? Was the abortion late in term? Scar tissue would have to be substantial to create a situation like this and the ONLY time I've heard of that happening is if A. you had an infection following the abortion and didn't seek treatment or B. you've had multiple abortions (as in at least 3).
I'd get a second opinion. If it is scar tissue, they can sometimes remove that surgically. good luck
PS: again, this is very rare if it is the case!