Many opponents to Christianity deny Christianity for their offkey and several reasons. One of them is the thought that Jesus said the people standing there hearing Him would see Him return. The Moslems claim Jesus never did return in their generation like He said He would. They are not locked into dispensationalism, and plainly read what we also claim Jesus said. But the fact is that HE DID RETURN in that generation, and they misunderstand how God came many times in Old Testament days via judgment using heathen armies and nations to afflict Israel, as in
Isaiah 10, for starters. Dispensationalism shoots it's own foot by making false interpretations of Christ's words that even non-Christians can plainly see referred to the generation Christ lived in.
The problem arises when dispies take what they think Christ meant, without any regard for the manners of speech used primarily throughout the Old Testament in ways that are apparent (when studied) to not have been intended to be taken as dispies take them.
So, like SneeKee implied, intentionally or not, it is quite a real ironic
strawman argument to take Christ's words, misinterpret them and say they were not fulfilled in AD70.