Op-amp with compensation has positive feedback with over-unity gain
Cipocip - the phase of the loop gain does not assume a value of 180deg between those two frequencies. You must not look at the asymptotic lines only. The real magnitude of the loop gain does not have a roll-off of -40dB/dec. This is true because (a) the open-loop gain of the opamp and (b) the rise of 1/beta both never reach 20 dB/dec (corresponding to a 90deg shift). As you know, each first-order system has a phase shift of 90 deg for infinite frequencies only. In the present case, the situation is even less critical because the 1/beta function has a pole (following the zero). Hence, the maximum phase shift will be (perhaps) only 75...80 deg. - dpending on the distance between both frequencies. 

More than that, a clear picture of the stability margin can be gained looking at the NYQUIST plot for the loop gain. The critical point never is encircled.