Depends on the circumstances. You DEFINITELY don't want your SWAT team to walk in all announced and relaxed to a hostage situation. Goodbye hostages. And all you're likely to get in terms of information on it is one random phone call until you're there. Same goes for bomb threats and such - if there's a suitcase sitting in an airport, they don't assume someone forgot it. Until further notice, its assumed a bomb, just to be safe.
No, this doesn't mean running in guns blazing, it does mean if the innocent victim in this case reacts violently or in a startling manner, which could happen due to shock, and the police react by shooting him believing it to be an attack, as that is what they have been informed it is, that it may count as reasonable force. It depends on the circumstances.
And what if, instead of seeing a guy sitting there playing games, they see the guy's brother walking out of the kitchen with a bloody knife from cooking dinner. Its not just one person in these houses, and you're going in fully assuming the worst, as if you don't assume the worst and it is an actual emergency, you have failed your job and people are dead.
You've also got to take into account, if someone's playing an FPS like Battlefield that tries to have as realistic sounding weapons as it can... How are the police supposed to react to what sounds like gunfire in a supposedly armed hostage situation?
Yes, if they walked in, and came to a guy's wide open living room and saw him sitting there playing games, and shot him on sight - that'd be excessive force, and there'd be and someone would likely be put on suspension at the very least. The problem is that that won't be the situation 100% of the time. There will be other exacerbating factors that could lead to a policeman opening fire, and if that happens, there is a chance it could have been reasonable, depending on the circumstances. In those cases, it is 100% the fault of the person who made the SWATing call. Even in the cases where it is excessive force, it is 100% the fault of the SWATter that the person died, the police would still have their inquiry and suspension and such, but it is still the SWATter's fault. If not but for the action of the SWATter, no harm would have been delivered to the injured party. It is also a reasonably foreseeable consequence of sending a battalion of fully armed men into a supposedly deadly situation.
Yeah, its horrible that someone could die - but the reality is it can happen, and not just because a policeman is trigger happy. It is something a SWATter should be fully aware could happen, and they probably are fully aware it could happen, and if it does happen, they should have to deal with the consequences of having a reckless disregard for human life in a civilised society.