Or subjects that have thorns.
We cannot discuss anything
If we are treading on corns."
-- I just made that up.
If everyone takes the discussion or debate in the right spirit, without ad hominem, separating the opinion from the person holding it, and agrees that there will be as many widely differing viewpoints as there are agreements....there are no sacred cows, thorns or corns to worry about.
I call this photograph "The Absent Tailor"