1) A golf/movie/pineapple/etc forum is social media.
2) I don't see anything wrong in posting about it on here or any other social media platform.
On the subject itself, you're not alone in this - check out Twitter for several people in the same boat. I had tickets booked for the Augusta National Women's Amateur, held the weekend before The Masters. Some things to consider:
Coronavirus isn't YGT's fault.
YGT like most travel companies are probably going to be completely screwed by this situation, and will be lucky to survive it.
Also worth considering:
Coronavirus isn't the customer's fault either.
I've now paid for a service/product that I'm not going to get.
The world does seem to be falling apart at the moment, but it also seems to me that YGT are simply not fulfilling what is required of them in pretty much all of these scenarios - a full refund if one is requested.
Taking a voucher seems like madness, in my opinion. As said earlier, they will be lucky to survive this. The timing for them couldn't be much worse either - at a guess, March-April must be the most popular time of the year for British golf travellers.
I will probably end up going through travel insurance, which I don't want to do - my premiums will probably go up, I would guess without checking that there will be some sort of excess involved, and YGT will have my cash for doing pretty much nothing.
However, I will almost never use them again, and I will also make sure I leave a review on every platform available to let people know that if things turn sour, YGT won't help you out. One bad review won't impact them, but if everyone who has been caught up in this leaves a negative review...