| While you never know who's armed and who's not
This may be true, but if the person has no history of violence, isn't wanted for a violent offence, has no registered firearms, and is not known to have any radical anti-government / Michigan Militia-type views, then there is probably no reason for such an armed assault.
| in these cases they're probably just as worried
| about the destruction of evidence
So a group of men armed with assault rifles is necessary to prevent destruction of evidence, because a couple of agents armed with handguns would have encouraged resistance?