Any privately owned enterprise has the right to choose which forms of payment they accept. Unless the government owns and operates this business then they do not have to. There is no problem with assistance but forcing companies to accept it is not constitutional at all and lets to government overstep their boundaries.
I think in the long run it hurts companies, if for nothing else than the loss of goodwill. But if they don't want to accept people through government assistance programs that is up to them. There are costs associated with administering the program on their side too, and they may not want to spend that money.
No, companies should not be able to deny people government assistance. In certain industries, government assistance programs should be mandatory for companies to follow. After all, the government programs exist for a reason. If all companies decided not to participate in the programs, then the programs would be rendered useless.
I do not believe that corporations should have executive decision making powers over their participation in federally mandated assistance programs. If these companies are American companies, they should adhere to federal laws and regulations. For example, AT&T provides communication services. No one should be restricted from their ability to communicate because they're unable to pay an $80-$100 phone bill monthly. Additionally, if such companies are willing to offer discounts due to a customer's place of employment, then they should be willing to offer discounts to low income customers as well.
No, companies should not be able to choose with government assist programs they accept. These programs are in place to prevent companies from taking advantage of poor people in the first place. If companies then get to choose which ones they believe in, the entire program infrastructure will be undermined.