Air carrier Captain reported a conflict with an aircraft on the runway while on final approach and with a landing clearance during night conditions. The Captain performed a missed approach; informed ATC of the aircraft on the runway; then returned for a landing.

Narrative

We were cleared to land on runway 08R. We noticed aircraft on runway. I informed the first officer who was flying that we would commence a missed approach if the aircraft did not clear by the time we reached our DA which was 450 feet. I mentioned this at 1200 feet and he left the automation on because of this as previously briefed. The aircraft was still on the runway and I called go-around. I notified the tower. They did not reply. We proceeded with the published procedure. I notified the tower a second time when they seemed confused and ask why and if it was because we were unstable. I told them there was an aircraft still on the runway and he said that was not the case. Then asked what I was doing and what heading I wanted to. We were already on the published missed approach and heading 270. Everything after that was uneventful.Cause: This was caused by the tower not recognizing an aircraft was still on the runway and too close to be safe. I probably used the terminology of Aircraft X going around instead of saying commencing a missed approach and.Either way it is very disturbing the confusion of the tower of not knowing the closeness of the aircraft and lack of communication. All three pilots on the flight deck saw the aircraft on the runway when we reached 450 feet. And commenced the missed approach.Suggestions: This situation happened at XA:00 local time and the airport did not seem busy. Not sure if there was internal distractions but operating a widebody with such close proximity to a previous landing aircraft is not safe. He actually tried to have a discussion about it when I said the reason. Also inappropriate.