With respect to the existence of this and that (or non-existence), etc., I often have the feeling that these discussions are just ways of detracting away from the main business of work (that is, when they occur in linguistics dis[c]ussions rather than in philosophy). There are certain places where a certain consensus can be found (philosophically), although there are of course always discussions and debate (that is the usual business of philosophy after all). It seems of limited use to put those debates at the centre of discussion when we discuss linguistic method, even though the texts that are thereby produced might sound deep.
 To be clear, ideationally, 'existence' and 'non-existence' are construals of experience as processes of 'being', reconstrued metaphorically as things. Interpersonally, propositions that predicate what does or doesn't exist are assessed as valid or invalid according to the criteria that are held to be valid in a given cultural context. For example, much of what is deemed valid in science (systematic knowledge) is not deemed valid in fundamentalist religion (literal readings of mythic metaphors).
Because the field of philosophy is realised in language, the SFL model of language can be used to reconstrue the meanings of philosophy in terms of the metalanguage. See, for example, any of the reconstruals of philosophy (or science or mythology) through SFL theory at Informing Thoughts.
 To be clear, it is Bateman himself who is most responsible for raising questions of existence in Sysfling discussions, and so it is Bateman himself who is most responsible for the distractions away from what he defines for us as 'the main business of work', and so, for producing the texts that "might sound deep"; see