If you guys didn't think that it was embarrassing enough to justify with "But Trump" then you would not have done a "But Trump," as there would be nothing embarrassing to try and justify.
Sigh. There are two separate points here. I genuinely can't work out if you really don't understand this or are just pretending not to
Point 1 is - no, I don't find someone making a mistake in a speech or a word slipping their mind embarrassing. I do it, so do you, and so does everyone. And Trump certainly did. Which brings us on to...
Point 2 - why are you declaring Biden embarrassing for doing this when you've spent the last 4 years defending everything Trump has done when he did the exact same thing and many things significantly more embarrassing during his tenure? It's a rhetorical question of course, we know why. It's because the standards you judge someone by depends entirely on whether you agree with them or not.
The next time Biden does something embarrassing you will also "But Trump", simply because Joe Biden is an embarrassment and you have no good defense.
Well, again, embarrassment is subjective. But yes, the next time you declare something Biden does as embarrassing when there are plenty of examples of Trump doing the same thing which you didn't declare an embarrassment or even defended then we will point out your hypocrisy again.
The way to take out the subjective factor is to look at data across populations. I have supplied that data which shows that Biden is more popular within the US than Trump ever was and that in multiple other countries Biden is significantly more popular than Trump. You may find Biden an embarrassment but many don't.
And if you fancy a bit of introspection you might want to consider why you repeatedly defend one person for doing something and then criticise another person for doing the exact same thing, apparently based entirely on whether you like that person and what they say.
Try to be a bit more objective if you want to be taken seriously.