On Thursday, February 25, 2021, I was on board Flight #3514 ready to depart at 8:45 a.m. for my flight to Oakland, CA from Indianapolis, IN. I was traveling to visit my son, daughter-in-law and my grandson. I was masked-covered, sitting in my aisle seat and reading an opened newspaper in front of my face when a black, male steward came up to me and told me to cover my nose with my mask. I was actually unaware that my mask had fallen as I could still feel it on my nose but apparently it was just touching my nose instead of covering it. It was, however, covering my mouth. I do not remember saying anything to the individual other than a possible "OK" as I adjusted the mask up over my nose and continued to read my open newspaper. No other expression was indicated, etc. as I am aware of the rules and genuinely felt that the fact that my mask had slipped, albeit still over my mouth and touching my nose, was indicative of the fact that I was essentially in compliance, especially after I immediately did raise the mask up as requested. However, approximately a minute or so later a white female approached me and told me that I had to "rebook my flight". (This lady apparently came from the terminal as she was not an attendant and handled the flight change thereafter.) I naturally inquired as to the reasons why and was told essentially that this was the captain's orders based on the wearing of my mask. Further discussion led me to understand it was because my mask was not over my nose, although it was after I had been informed to raise it a bit just the one time. The mask was being properly worn at the time the lady approached me. Despite my incredulousness over this alleged incident, I did leave the aircraft without any overt or negative issues although I did complain that my mask was up, that I had only been asked the one time to raise it and that this was certainly no grounds for me to have to be rebooked. Obviously, there was no reversal and I had to rebook my flight which meant a six-hour wait till the next flight and my arrival in San Francisco instead of Oakland. (My son was definitely inconvenienced in conjunction with the fact that I wasted six hours in the airport and was six hours overdue with him and his family.) In hindsight, I remembered the flight attendant staring at me from his position standing at the front of the seating prior to confronting me with his only request but since I was not aware of anything improper and was reading my opened newspaper, I didn't think any more about his facial appearance or his oversight. It wasn't until he came to my aisle seat that I was aware of what I had been allegedly doing improperly. I feel that this instance was WAY overblown, that this may have been a personal issue, now boarding on reverse discrimination by this black attendant for some unknown reason. Perhaps it was an age thing: I am 69, he may have been in his early thirties. I cannot think of any other reason why I was treated in this manner as my mask wearing was NOT egregious in itself and was corrected immediately upon request, without any comment other than a possible "OK". By the way, I noticed several passengers on the subsequent flight from Phoenix, AZ to San Francisco, and the two flights on my return trip March 1 where other passengers were not wearing their masks correctly, some with the mask even below their upper lips. There were no warnings or resultant corrective actions taken with these folks, a non-action somewhat expected from a common sense point of view, at least as far as being rebooked. The individuals wearing their respective masks improperly continued off and on throughout the flights absent any intervention by Southwest Airlines personnel. I realize that on an aircraft the captain's word is absolute so I do not believe he was aware of anything other than what was told to him by the attendant re: my mask. Thus, his response was to have me removed from his aircraft, not wanting any "trouble" but certainly not knowing the facts or the truth behind the alleged issue. As an aside, my profession has been within the legal industry since 1975 and I have been self-employed in such since 1992 so I am well aware of laws, truthfulness and other people's ulterior motives. Thus, my conclusion that this simple issue was race-related although I have no idea why other than perhaps some pre-existing issue with this attendant. I certainly didn't have any issues with him or anyone else, regardless of color, gender, etc.