Block or ignore someone on Hangouts who only sends me group messages (spam)?

According to Hangouts Help:

Users who do not know you need to send an invitation to chat. To protect yourself, Hangouts filters spam invitations into a separate screen. If a spam invitation is not filtered or if you do not feel comfortable in a Hangout with someone, you can block it. When you block someone, he can see that you are online but can not send you Hangouts messages.

However, this statement does not seem to be true because someone constantly sends me spam on Hangouts via a group chat. I have never accepted invitation from this person to discuss. I've tried leaving the group and archiving the conversation, but I still get those messages. The help article explains how to block a person, but it only seems to work if that person sends you direct messages. I can not block someone who only sends group messages.

Block somebody

  1. On your computer, go to Hangouts at hangouts.google.com or Gmail.
  2. Select the person in the Hangouts list to open the conversation.
  3. At the top of the conversation, click Settings.
  4. Click Block, and then click Block.
  5. If you want to remove someone from your list, but do not want to block it, open the "Contacts" tab, point to the person's name, click More, and then click Hide. [contact name].

I can not follow these steps because when I click Settings for Group Chat, there is no option for Block. I can only Let or Archive. As mentioned above, the selection of these options did not prevent this person from sending me other emails. I do not have any individual conversation with this person. How can I block them?