Jack is demanding an extension of the right of self-determination to ethnic communities. There is a big difference between nations and ethnic groups. The second is a group of people who share only some of these characteristics. They could be based around a common faith, descendants, race, roots in another country, languages, customs or cultural manifestations. In many societies some social classes, occupations or strata have overlapped with what are today considered ethnic groups.
Every nation has many ethnic groups or communities.
Britain has hundreds of them. However, we are not in favour of giving them the right to form their own state. There are tens of thousands of ethnic groups all over the planet and it is simply impossible to advocate their right to form sectarian, ethnically-based states which would create several other problems. When 'rights' for some of these communities could mean trampling over the rights of other communities, we are not going to back them. For instance, we do not defend the right of the white British to put quotas on coloured people or immigrants.