"Would you accept four different guys calling themselves the Beetles, also?"

There is a big difference (aside from the spelling).

The Beatles broke up in 1970. End of story. The Kingston Trio kept going (aside from the few years off). The story continues with new chapters and characters and links to the past.

If a group gradually replaces members and continues on, I see no reason why they shouldn't continue to use the name. Haworth and Grove have put their time in with the group, especially Grove. It is not like three new members have suddenly appeared on stage.

Please don't get me wrong, I do see your point. For me personally, I am not as bothered by it since I do see a body of work that has been built in more recent history that deserves to be kept up.