the idea that there's no possible way to reasonably estimate the number of environmental activists seems very unlikely to me.
Do you happen to have some sources for a reasonable estimation on the number of, say…
• hackers?
• crackers?
• political activists?
nope. What has that got to do with my comment? Someone was implying that it was impossible, I was saying that claim was implausible. People estimate those kinds of numbers all the time for statistical purposes.