Per meta:Deletionism, few editors use this word as an unironic self-descriptor, and it is more often used as a slur. Per WP:AGF, WP:CIVIL and WP:NPA, use of such slurs is to be avoided.
Most editors who disproportionately !vote "delete" or "redirect" AFDs probably only do so because they rarely participate in AFDs except when they themselves come across an article that should probably be deleted in accordance with our deletion policy (which is not, it should be noted, subordinate to any of the notability guidelines), not because they are secretly planning to destroy the encyclopedia. When arguing about "deletionism vs. inclusionism" may in fact be arguing against the very concept that AFD is a battleground in response to their having been accused out of the blue of being a "deletionist". This is another reason why calling other editors "deletionists" is disruptive.
One possible exception to this is the use of the word "deletionist" to mean "an editor with a focus on article deletion rather than on this or that topic".[1][2] Such editors, ironically, tend to be "keepists" rather than "traditional" deletionists.