You did not ask anything of the sort
Oh, I was confused by the question mark. I may have already had some assumptions about your reasoning but the question was in fact asking why you thought that.
So tell me this: How can you recommend anything?
That is a fair enough question. There are probably several ways. Some are probably better than others. If it is for someone you do not know and have no clue about their size, strength, experience with firarms, etc the best one can do is to recommend they try to handle different guns and see what feels comforatable in terms of handling and fit. Fit goes along way when it comes to felt recoil as well. An ill fitting gun can make recoil seem much worse. The other recommendation that is sound is that they try if possible to shoot various models. Beyond that one might offer opinions on guns that are widely viewed as reliable. If one thinks they can do more than guess at what model might be "best" in such a situation they are kidding themselves. That is why you so often see on this board the sound advise of go try them out, when people ask which gun.
If it is someone I know, I get out my guns (and often invite some people I know who have a bunch of guns) and go to the range and let them shoot them. This is much more useful than telling them what I like. I have at times been rather surprised by what someones preferred gun was at the end of the day.
Yes, there are 300# women weightlifters who can handle a 12 ga. with one hand. Yes, there are 100# men who can't. So What.
I would contend that the extremes are not forcedly where one finds women who are proficient with a 12 gauge or men who might benefit from a smaller bore. Do you honestly believe that it is?
I gave my opinion based of fact
You gave your opinion, and it might well have been based on a fact. The problem was that fact has little bearing outside of its specific context. Re-read my above post about the worth of an opinion based on one female shooter's experience with one particular shotgun.
Some facts are not a good basis for offering advice. It is a fact I fired a scandium framed .357 and didn't find it objectionable. It would not be good advice percipitating from that fact to say that recoil is never an issue with scandium frame .357s. It is a fact that I like my semi for home defense more than my pump guns. That in and of its self is not a good basis for me to say Semis are the way to go for anyone who wants a HD shotgun.
Further your fact (one woman found the recoil of a 20 to be too severe) is a horrible basis for your opinion (women should have 410s) not only for the sample size problems already mentioned but because you offered no support for the idea the the gun being a 20 gauge was really the problem. There are issues of fit, the weight of the gun, etc that could be the more proximate issue.
Just as you can posit your opinions, I can explain why I think they are invalid and ought to be ignored by those looking to glean info from this thread. You can also explain why I am wrong. I have a feeling, based on the parts of my post that you decided to respond to that you will not attempt to do so.