Even you don't breastfeed baby, you may still transmit flu to baby, flu is transmitted through air but not breast milk!!! So you should think of how to prevent transmitting the virus to baby next time,say by wearing mask, but not whether bf baby or not. If you keep breastfeed baby, you can help him to recover better and faster, so why not?
The most important thing is whether you want to continue to bf baby or not. If you believe that bf is good, then never mind about what other people said. They'll never understand. You are the one who make the final decision!!!
If you give up just because what other people said, then I think you'll regret very soon afterward, as everybody know mama milk is the best for baby!!!
Keep up and don't be upset, all BK bf mama are supporting you!!! You baby will be well very soon.