Q:

Can we trust phrases on T-shirts as valid and sensible English sentences?

Someone asked me about the meaning of 

I love second rate of sun

He says he saw it on a T-shirt (in Iran)
What could be the meaning of it?! Should we trust such sentences or they are more some cool phrases on T-shirts which may have not a sensible meaning?!

Update: some says that people do mistake and we can't trust any sentence, I know! but my main question is that is it possible that people (even native) deliberately use some irregular or even non sensual phrases as fashion (on cloths or etc.)!
To me, it is important to know because when I see some weird styles, I wonder if my English is not that good to understand the phrase, but if I doubt it could be a deliberate out-standard sentence I less question my knowledge of English! 

A:

Can we trust phrases on T-shirts as valid and sensible English sentences?

No, of course not. There is no government T-shirt Grammar Department regulating t-shirt designs to ensure they make sense.
More broadly:

Can we trust phrases [that we see or hear anywhere] as valid and sensible English sentences?

No. People make mistakes. People use bad grammar on purpose for effect. Even books about grammar sometimes contain grammatical errors.

I love second rate of sun

This doesn't make any sense in English - unless "Second Rate Of Sun" is the name of a band or something like that, in which case the phrase "Second Rate Of Sun" doesn't seem to make any sense itself, but the phrase "I love Second Rate Of Sun" would make sense.
Given that this was seen on a t-shirt in Iran, I would guess that somebody got a translation into English wrong.

