The weight of the glove is an indication of the amount of padding there to gradually decelerate your fist and transfer the impact energy gradually into whatever you hit. Extra padding takes longer to compress, and larger padding with more surface area spreads the impact to reduce the peak stresses and pressures. So, a heavier glove isn't more dangerous: the weight of the glove is insignificant compared to the weight of your body moving behind your punch. It's more like having one mattress between you and a punch versus having two or three: more is heavier, but the thickness spreads and softens the instantaneous forces making you safer.
If you google for "boxing gloves 8oz 12oz 14oz 16oz" or similar you'll turn up a few websites with tables for recommended gloves sizes according to your weight. I'm not going to endorse any particular site, but to summarise: only very light people should consider anything less than 16oz for friendly amateur sparring. If you're heavier/bigger, you may want 18oz or more.
(Regarding Force = mass x acceleration: what big gloves do is decrease acceleration - which is the rate at which the target's velocity is changed - by having about the same amount of overall change in velocity take place over a longer period of time. That happens because the thicker padding reaches the target earlier and takes longer before reaching maximum compression. By the formula, reducing acceleration reduces the instantaneous forces on the target.)