I wouldn’t say childish! A lot of people under the restricted voting age which clear intelligence on politics and their causes/effects are unable to vote. The reason this is an issue is because we will have to live with the long term effects that leaving the EU will cause for us - whereas people over the age of 50 who were the majority voting for Leave, mostly xenophobically. 
People demand a revote because of the idea that young people are going to have to live through a choice that we do not want. This is why it’s such an issue!