Although you can put treason and traitor in quotation marks or italics, the use of words like in the sentence to indicate that they are being referenced as words rather than syntactic entities means that you don't have to.
The use of quotes or italics is more common, but it's not essential in this construction.
Also, between quotation marks or italics, italics would probably be preferable because of the association of quotation marks with scare quotes which indicate irony or doubt.
Speaking of scare quotes, preceding treason and traitor with words like is the same sort of thing as preceding a word with so-called instead of putting it in quotation marks.
- There are many "sympathizers" who agree.
- There are many so-called sympathizers who agree.
You normally use one form or the other. The use of so-called means that you don't need to put sympathizers in quotes because you've already signalled its upcoming status.
From The Chicago Manual of Style (17th ed.), 7.59:
A word or phrase preceded by so-called need not be enclosed in quotation marks. The expression itself indicates irony or doubt. If, however, it is necessary to call attention to only one part of a phrase, quotation marks may be helpful.
So-called child protection sometimes fails to protect.
Her so-called mentor induced her to embezzle from the company.
These days, so-called “running” shoes are more likely to be seen on the feet of walkers.
Update: As requested in a comment, here is what Chicago (7.63) says about words as words specifically:
When a word or term is not used functionally but is referred to as the word or term itself, it is either italicized or enclosed in quotation marks. Proper nouns used as words, as in the third example, are usually set in roman.
The term critical mass is more often used metaphorically than literally.
What is meant by neurobotics?
You rarely see the term iPhone with a capital i.
Although italics are the traditional choice, quotation marks may be more appropriate in certain contexts. In the first example below, italics set off the Spanish term, and quotation marks are used for the English . . . In the second example, quotation marks help to convey the idea of speech.
The Spanish verbs ser and estar are both rendered by “to be.”
Many people say “I” even when “me” would be more correct.
There are no hard and fast rules, but there are general guidelines. You will find exceptions to most things. Comprehension and consistency are the key points.