Answer
Yes, in both GoToMeeting and Zoom the chat can be disabled.
In Zoom, the chat can be deactivated by clicking on "More" (the symbol with three dots) under "Chat" (or Alt+H). Afterwards, the option "No one" can be selected under "Allow attendees to chat with". It is also possible to restrict the chat to communication with hosts by selecting the "Host only" option.
It is generally not recommended to completely deactivate the chat in meetings, as it can be helpful as a backup communication channel.