Yes, it’s not much different from tipping. Puts the burden of responsibility in the wrong place. If a business wants to support charities and use it in marketing, just give money to charities and tell people how much it was. And/or give people the contact details of the charities if you want to promote them.
Absurd that pointing guns at people to get fake support would be seen as any more legitimate than just having the soldiers do the fake voting themselves.