Why is Meetup.com allowed to have ownership rights of a very common English word that simply describes the service they provide?

According to Meetup.com's trademark guidelines, 'The word "Meetup" and the other Meetup Marks, such as our Logos, designs, slogans and names are registered trademarks or trademarks of Meetup, Inc. in the U.S. and/or other countries.'

IANAL, but to me, this seems highly anti-competitive because it suggests they could sue anyone who uses the word "meetup" to describe a... meetup. Or sue a competitor that called themselves "FantasticMeetups.com" for example.

See:

1. http://www.mbbp.com/news/generic-trademark

2. https://help.meetup.com/hc/en-us/articles/360001655932-Meetup-Trademark-Guidelines