And B. he was right that capitalism was much better than its predecessors. Your vision of 'a worldwide massacre' tells us more about your frame of mind than it does about the world. How could you discount all the marvellous and creative things those six billion fellow human beings get up to, even under the admittedly chaotic, wasteful and occasionally barbaric system of capitalism?
Such an overwhelmingly pessimistic view is itself reactionary, and, strangely in keeping with the ideological outlook of capitalism today, which is preoccupied with gloom and misery. It is the contemporary equivalent of the reactionary Christian message of original sin, fallen man and the end-time.
a. Marx saw capitalism as opening the possibility of socialism; whether he _also_ thought that in and of itself it was higher, better, superior social form than prior forms is debatable.
b. But if he did think that, he was wrong. (It is not even wholly obvious that capitalism was a precondition for socialism, but that is another debate.) In any case the progressive features of capitalism have long been exhausted, socialism being now further away, more doubtful of achievement, than it was 50 years ago. [Note that by "progressive" I mean that which points towards a qualitatively superior future possibility, independently of the present goodness or badness of the event in the present.) For two centuries now we have been in the midst of a worldwide massacre, a massacre which shows signs of rapidly expanding, far from diminishing.