The flag is a symbol for government, plain and simple. https://www.law.cornell.edu/uscode/text/4/chapter-1
Big Government people of any stripe believe that government itself is sacred, regardless of how they treat its various symbols. The offices, "public places," and boundaries it claims to own are venerated religiously. Its privileges are treated as natural rights, while natural rights are impugned. This religious veneration must be rejected utterly. It is idolatry.
The government represented by that flag violates the natural rights to life, liberty, and property on a daily basis as a necessary part of its operation. This applies to all governments. I'd burn a Canadian flag, the Stars and Stripes, the Confederate Battle Flag, the EU flag, the Israeli flag, the Saudi Arabian flag, the Chinese flag, or any other with equal disdain.
If you buy a bit of cloth, it is yours to use as you see fit unless you violate the life, liberty, or property of another. It is utterly irrelevant whether it has a flag pattern of some sort, it is a t-shirt from a rock concert, or a bedspread, or anything else. It is yours to use and dispose of as you see fit. that is what liberty and property rights mean.
Even if the flag somehow still stands for freedom despite all this, the principle is not harmed when people use their own property as they see fit, even when they "desecrate" the symbol of freedom.
I realize people have the right to burn the flag, I'm just saying I don't like it when they choose to do so, and I have explained why. I think that we are just going to have to agree to disagree.