Guinness, being black and white, indicates you have a tendency to see the subject matter of the dream in black and white terms. This comes across as being intolerant or extremist. You see others as either being with you or against you. There is no neutral position allowed. You need to be more tolerant.
Holding a Guinness in your hand means you are holding onto a black and white attitude. Read the description for Guinness above and ask yourself: “are you aware that you are doing this but still refusing to change?”