Yet another allusion to computer lore; in this case, Edsgr Dijkstra's 1968 notorious polemic paper GOTO statement considered harmful, which launched a revolution in structured programming. The phrase is used when someone knows they are saying something which may prove portentous --- but is likelier to be regarded as pontifficating.
See also Jargon File entry: http://catb.org/esr/jargon/html/C/considered-harmful.html