attacking stronger stacks

i'm having a discussion with someone about attacking stronger stacks, in my opinion its pointless, my discussion partner claims he has a strategy behind it.

Are there any situations where it would be intelligent to attack stronger stacks?

the only one i could think of is in a same time capital game i won where i attacked a 32 stack with two stacks of 17 and 19, i thought the numeric advantage + 3:2 odds made it smart.

Fixed card games that have been going on for waay too long.
Someone that is waay too strong and needs to be brought down by two people - so one of them attacks first, and then the other finishes it off.

These are the easy cases, there might be others. But usually it's the smart thing not to lose troops yourself, and that means that usually it's the smart thing not to attack, even if you have more troops.

Maybe in a team game, you see the enemy fortified his partner to build a stack by your teammate so that they can attempt to take them out next turn. So to save your teammate you can weaken the stack

attacking a larger stack does not have to be solely for conquering it. Another reason to weaken a larger stack, besides saving a teammate, could be in a regular deathmatch with multiple players and it's in your best interest to prevent that stack from eliminating another player for their cards and overwhelming advantage. For the chance to stay alive in the game this way, the loss of troops is worth it. Stacks are dangerous, and the strongest players typically try to build one, in fact, more than one if possible even around the MAP both for survival (not being eliminated) and for the opportunities, which come frequently, to eliminate a weak player. I can see the wisdom of a smaller stack attacking a larger stack to prevent someone running through everyone on the MAP with cards. e.g. Losing 5 to 8 is worth preventing people gaining 20, 25, 30 etc in cards.....

Be really careful with that though, it's very, very easy to overattack in order to "balance" the game, and instead ruining it.
If you want to stop someone from running the board, it's usually better to protect the weak players, rather then to weaken the strong players.