Let me see if I can take a swing at it. I'm not sure I actually buy these arguments, but at least it might be a place to start.
One of the best arguments for deflation is technology and demographics. I think this piece is a pretty good piece around this is: https://www.youtube.com/watch?v=F8lfLqnhuGs
A over simplified summary would be if we automate more and more things, either due to a lack of people or simply due to "progress" (e.g. lower costs) you can do more with less. If everyone started to live at home, cooked all their own meals and work remotely (roughly our current world), then you need less oil and have more spare humans looking for work. Thus the price of a human's hour goes down. Since humans have less money and the cost of manufacturing has gone down, over time prices are forced down. In a sense there might be rapid simplification of job roles as fewer roles need humans and so humans are forced to solve problems on their own.
Now you add in a mad man printing as many dollars as possible, trying to stimulate demand. While some, particularly those interested in becoming rich might grab fists full of dollars, many might be contented with the simpler lifestyle. Think millennials not buying their own car (a ~20k purchase every 10 years), instead using their phone (a ~.1-1k purchase every 2-4 years), Uber and public transport. Unless you believe public transport is more expensive than owning your own car, that would appear to be deflationary. Think elderly people who tend to stay home and spend less. "Retirement experts" estimates suggest 20-30% less spending by the elderly. So if the west has a demographic bubble of people entering elderly stage and choose not to grab fist fulls of money, then you start looking more like Japan.
Add to that, when the elderly die they leave their stuff but their debt basically disappears. Granted some of that is repossessed, but that is only assets that have not yet been consumed. If birth rates are going down, then there is an excess of stuff, like housing for the number of people we have. See the mid west of the US. Since debt is leverage and leverage is just pulling profits from the future when that debt disappears, it is like a claim on a income stream disappears and thus the value of that debt becomes 0. That all seems deflationary to me. Basically, banks create magic money (i.e. fractional reserves) from thin air and then charge a fee for anyone to access it via debt. When that debt disappears, particularly if that debt was used for consumption and not production, some of the magic money disappears too.
The other argument I can think of is based upon Paul Krugman's arguments in the 2008 crisis, who described tickets used for baby sitting. You and your friends each have 3 tickets and they say any of your friends will watch your kids for a ticket and you will watch theirs for a ticket. If people just hold onto their tickets, fearing they may need a babysitter for a week, then no one spends. Printing "money" simply gives everyone more tickets, letting them feel safe in knowing they can have their kid watched for a entire week if needed. In such a case, holding more tickets doesn't equal more spending. That isn't deflationary, but it isn't inflationary. Now what if someone's child grows up and they simply quit using their tickets. That is deflationary. That is another way of looking at the demographics. What if more people join the club. You make more tickets, thus that is inflationary. The difference here is that in both cases it is not inflationary or deflationary per capita. GDP != GDP per capita.
I have heard that in Japan they had time-limited payouts when they tried to create inflation (thus trying to drive demand). There were an unexpected large number of people who let their payouts expire. This capture that difference between elderly and younger folks.
One last view requires I point out the obvious: Inflation is simply the price of goods goes up relative to the currency. Is inflation a personal view or a statistical basket of goods? I point this out because all the central bankers are printing like mad. The dollar might not "inflate" relative to other currencies, even if it does inflate relative to your personal needs. Thus betting on inflation might depend on how you count it. Will your dollar be worth less at Target? Yes. Will it be worth less in some forex trade? No.
While not directly related, you might enjoy: https://www.youtube.com/watch?v=GaWg-cuEHVs
Edited for clarity, I hope.