How do the phrases “herded together,” “barb of wire,” and “forbidding shapes” contribute to the meaning of the poem?

They emphasize the narrator’s recognition of the grim history the tourists are observing

The quotes are similar to phrases you would hear when people described what happened during the Holocuast. The Jews were "herded together" onto cattle cars and into concentration camps where they were held behind barbed wire. Depending on point of view, the "forbidding shapes" could be an image of the Nazi soldiers or the Jews. In the poem they refer to the continents.

the tone of the passage is sympathetic to the forbidden love of romeo and juliet. the nurse plays a significant role in the play. she is responsible for making their meeting again possible. additionally, there is a sense of warning in the choice of words of the nurse. she seems to be authoritative when she calls romeo "scurvy knave", and at the same time the fact that she addresses to him as "sir" reflects respect. the nurse is "vexed", this word describes her confused state of mind. on the one hand, she finds romeo a fine and eloquent man, but on the other, it is thought that man's nature forces men to try to trick women.